Seafloor Geomorphology as Benthic Habitat: GeoHab Atlas of Seafloor Geomorphic Features and Benthic Habitats

By Peter Harris and Elaine Baker

Seafloor Geomorphology as Benthic Habitat: GeoHab Atlas of Seafloor Geomorphic Features and Benthic Habitats, Second Edition, provides an updated synthesis of seabed geomorphology and benthic habitats. This new edition includes new case studies from all geographic areas and habitats that were not included in the previous edition, including the Arctic, Asia, Africa and South America. Using multibeam sonar, the benthic ecology of submarine features, such as fjords, sand banks, coral reefs, seamounts, canyons, mud volcanoes and spreading ridges is revealed in unprecedented detail. This timely release offers new understanding for researchers in Marine Biodiversity, environmental managers, ecologists, and more.

• Explores the relationships between seabed geomorphology, oceanography and biology
• Provides global case studies which directly focus on habitats, including both biological and physical data
• Describes ways to detect change in the marine environment (change in the condition of benthic habitats), a critical aspect for judging the performance of policies and legislation

• Language: English
• Publisher: Elsevier Science
• Release date: Nov 5, 2019
• ISBN: 9780128149614

Book preview

scheme.

Preface

Peter T. Harris and Elaine K. Baker

The first edition of Seafloor Geomorphology as Benthic Habitat: GeoHab Atlas of seafloor geomorphic features and benthic habitats was published in 2012. In February 2017 we were invited by Elsevier to consider editing a second edition. There was a perceived need for this new edition because of the speed at which the science has been evolving. Case studies in the first edition were based on data collected mainly between 2005 and 2010. The second edition provided an opportunity to present some of the extensive new data collected over the last ~10 years using new techniques and in different geographic areas. The 53 case studies included in this book represent the state of the art in habitat mapping science. They provide concise reports based on a consistent format that all authors followed, with references included for readers to follow up as needed.

The goals of the second edition are the same as for the original volume. These are summarized in Chapter 1 and include four main objectives: (1) to support government spatial marine planning, management, and decision-making; (2) to support and underpin the design of marine-protected areas (MPAs); (3) to conduct scientific research programs aimed at generating knowledge of benthic ecosystems and seafloor geology; and (4) to conduct living and nonliving seabed resource assessments for economic and management purposes, including the design of fishing reserves. A particular goal of the second edition was to add a focus on detecting change in the marine environment (change in the condition of benthic habitats). This is a critical aspect for assessing the performance of policies and legislation enacted by governments. The first edition had gaps in spatial coverage of case studies especially in the Arctic, Asia, Africa, and South America. Therefore, the second edition aimed to add new case studies from these unrepresented geographic areas.

This second edition has succeeded in achieving most of these goals. All of the case studies completed an assessment of the condition and trend of their study area, providing information that will be of direct interest and relevance to managers and decision-makers. The volume comprises 53 case studies contributed by GeoHab authors from around the world and we have achieved good representation from South America and Arctic regions. However, we have been less successful in filling the gap in Asia and Africa.

The end-users of habitat mapping science are a diverse group. They are environmental managers, ecologists, fishermen, seabed mining and petroleum explorers, conservationists, and other marine scientists. Our aim is for the technical descriptions to be self-explanatory to the nonexpert. The book is divided into three parts: Introduction; Case studies; and Synthesis. The introductory Chapters 1–6 (Part I) provide the reader with broad context and a basic understanding of the main concepts presented in the case studies; they might be thought of as an introduction to the science of benthic habitat mapping. A second purpose of the introductory and synthesis chapters (Parts I and III) is to link general concepts and geomorphic features with cross-references to specific case studies. The glossary is another important tool intended to assist our readers. It contains over 200 definitions of many technical terms used throughout the book, many of which were contributed by the case study authors.

A number of people assisted us in preparing the second edition. In particular we thank Debhasish Bhakta (UN Environment/GRID Arendal) for assistance with figures and maps and Hilary Carr (Elsevier) for editorial assistance. We hope this book will provide a useful reference for students, scientists, managers, and industry specialists working in the field of habitat mapping and that it will inspire further research and development of new methods and technologies to explore, better understand, and appreciate the seafloor and the creatures that inhabit it.

Part I

Introduction

Outline

Chapter 1 Why map benthic habitats?

Chapter 2 Habitat mapping and marine management

Chapter 3 Anthropogenic threats to benthic habitats

Chapter 4 Biogeography, benthic ecology and habitat classification schemes

Chapter 5 Surrogacy

Chapter 6 Seafloor geomorphology—coast, shelf, and abyss

Chapter 1

Why map benthic habitats?

Peter T. Harris¹ and Elaine K. Baker²,    ¹UNEP/GRID-Arendal, Arendal, Norway,    ²UNEP/GRID-Arendal, School of Geoscience, University of Sydney, Sydney, NSW, Australia

Abstract

This introductory chapter provides an overview of the book’s contents and definitions of key concepts including benthic habitat, potential habitat, and seafloor geomorphology. The chapter concludes with a summary of commonly used habitat mapping technologies. Benthic (seafloor) habitats are physically distinct areas of seabed that are associated with particular species, communities, or assemblages that consistently occur together. Benthic habitat maps are spatial representations of physically distinct areas of seabed that are associated with particular groups of plants and animals. Habitat maps can illustrate the nature, distribution, and extent of distinct physical environments present and importantly they can predict the distribution of the associated species and communities.

The data sets collected for constructing habitat maps provide fundamental information that can be used for a range of management and industry applications, including the management of fisheries, spatial marine environmental management, design of marine reserves, supporting offshore oil and gas infrastructure development, port and shipping channel construction, maintenance dredging, tourism, and seabed aggregate mining. Seafloor habitat mapping provides fundamental baseline information for decision-makers working in these sectors.

GeoHab (www.geohab.org) is an international association of marine scientists conducting research using a range of mapping technologies into the use of biophysical (i.e., geologic and oceanographic) indicators of benthic habitats and ecosystems as proxies for biological communities and species diversity. Using this approach, combinations of physical attributes of the seabed identify habitats that have been demonstrated to be effective as surrogates for the benthic communities that they typically support. Thus management priorities can be identified using seabed habitat maps as a guide. The work of GeoHab demonstrates how knowledge of seabed properties can be employed to guide marine environmental management, marine resource management, and conservation efforts.

Seafloor geomorphology is one of the more useful of the physical attributes of the seabed mapped and measured by GeoHab scientists. Different geomorphic features (e.g., submarine canyons, seamounts, atolls, fjords, etc.) are commonly associated with particular suites of habitats. Knowledge of the geomorphology and biogeography of the seafloor has improved markedly over the past 15 years. Using multibeam sonar, submarine features such as fjords, sand banks, coral reefs, seamounts, canyons, and spreading ridges have been revealed in unprecedented detail. The case studies presented in this book represent a range of seabed geomorphic features where detailed bathymetric maps have been combined with seabed video and sampling to yield an integrated picture of the benthic communities that are associated with different types of benthic habitat.

Keywords

Benthic habitat; potential habitat; seafloor geomorphology; biogeography; benthic communities

Habitat is the property that inherently integrates many ecosystem features, including higher and lower trophic level species, water quality, oceanographic conditions and many types of anthropogenic pressures. Thus, strengthening assessments of status and trends in habitat quality and extent will be an important priority in the development of a global marine assessment.

Assessment of Assessments Report, UNEP and IOC-UNESCO (2009)

General outline of the content of this book

This book provides a synthesis of seabed geomorphology and benthic habitats based on the most recent, up-to-date information contained in 53 case studies. Part I (Chapters 1–6) of the book provides an introduction in which the drivers that underpin the need for benthic habitat maps are examined, including threats to benthic habitats. The habitat mapping approach and classification schemes, based on principles of biogeography and benthic ecology, are reviewed and the use of biophysical surrogates for habitats and benthic biodiversity are surveyed. Part I ends with a brief summary of seafloor geomorphology and geomorphic features that are the subject of the case studies. The case studies are cross-referenced throughout Part I, to provide the reader with a broad overview and context for the detailed information they contain.

Part II (Chapters 7–59) of this book includes 53 separate case studies representing a diverse range of geomorphic features and their associated habitats from the coast to the abyss around the world (Fig. 1.1). The spatial content of the case studies, combined with the review of information provided in Part I, warrants the description of this book as an Atlas in the sense that it comprises a collection of maps that represent a range of different geomorphic features and habitats. Spatial mapping is one of the most important tools used by GeoHab scientists to convey information and demonstrate relationships among different variables.

Figure 1.1 Distribution of 57 case studies presented in Part II of this book. Chapter numbers are indicated for each case study.

To be accepted, case studies had to conform to a template. Case studies are required to contain both geomorphic and biologic data, provide a clear description of at least one geomorphic feature type, describe the oceanographic setting, and provide an assessment of the naturalness (state and trend) of the environment. The spatial comparison of biological data with spatial physical data is a key element of every case study and authors were given the opportunity to describe surrogacy relationships and the methods used to identify and quantify them. A glossary is included with this book to provide definitions of key terms used in habitat mapping, description, and classification.

Part III (Chapter 60) provides a synthesis of the content of the case studies and is partly based on responses to a questionnaire that was completed by case study authors; responses to the questionnaire are also considered in the introductory chapters (Part I). The synthesis (Part III) includes headings such as attributes of the case study areas (depth range, naturalness, geomorphic feature types), surrogates and classification systems used, the socioeconomic aspects underpinning habitat mapping (main clients for habitat maps and funding sources), gap analysis (i.e., geographic areas, geomorphic features, and environmental variables not included in the case studies), and finally what constitutes best practices for habitat mapping.

What are the main purposes of habitat mapping?

When asked this question the case study authors nominated a number of purposes for mapping benthic habitats (Table 1.1), but among these four stand out as being preeminent: (1) to support government spatial marine planning, management, and decision-making; (2) to support and underpin the design of marine protected areas (MPAs); (3) to conduct scientific research programs aimed at generating knowledge of benthic ecosystems and seafloor geology; and (4) to conduct living and nonliving seabed resource assessments for economic and management purposes, including the design of fishing reserves.

Table 1.1

Many authors nominated more than one purpose for their study. See Fig. 1.1 for location of case studies.

An important point is that many authors nominated more than one purpose for their case study (Table 1.1). This highlights another particular benefit of habitat mapping: the data collected to manage one sector can be applied to others, since most of the information required about habitats is essentially the same for all applications. The goal to "map once—use many ways" underpins and justifies most government-funded seafloor mapping programs as well as the creation of national and regional databases and information systems containing essential marine environmental data.

What are benthic habitats?

A habitat (which is Latin for it inhabits) is an ecological or environmental area that is inhabited by a particular species of animal, plant, or other type of organism. Benthic habitats are physically distinct areas of seabed that are associated with the occurrence of a particular species. More broadly, habitats are often utilized by communities or assemblages that consistently occur together (e.g., shallow, wave-influenced rocky seabed, kelps, mollusks, and fish occur in a kelp forest habitat; Connor et al., 2004). The collective term biotope is commonly used with reference to both the abiotic and biotic elements (physical habitats and their associated biota). The benthic habitat includes the natural environment in which an organism or community lives, or the physical environment that surrounds (influences and is utilized by) a species or community.

The classification of habitats may be structured in a hierarchy to reflect degrees of similarity (e.g., biotopes, biotope complexes, broad habitats). Seascapes (the marine version of landscapes) comprise suites of habitats that consistently occur together. Chapter 4, Biogeography, benthic ecology, and habitat classification schemes, of this book contains more detailed descriptions of the fundamental concepts of biogeography and habitat classifications arising throughout this book.

Potential habitat mapping

In order to truly understand the spatial relationships between the occurrence of organisms and their preferred habitats, information should be collected about both. However, the available mapping technologies generally reveal only the physical aspects of the marine environment and, at broad spatial scales, they do not provide much information about the occurrence of individual organisms. In other words, our ability to map the physical spaces that organisms might utilize far exceeds our ability to measure the extent to which those spaces are actually occupied.

Mapping the physical habitats is commonly known as the potential habitat mapping approach (Greene et al., 2007). The data contained in the Ocean Biogeographic Information System (Fig. 1.2) makes a clear point. Although the database is already extensive and contains over 30 million records, there are still large gaps in the registration of species and we will never possess perfect knowledge of the existence of species or of their spatial distribution. It is impossible to map the ocean’s true species biodiversity. However, using potential habitat maps based on relationships that have been tested in different settings, we can at least estimate biodiversity and make predictions about its spatial distribution.

Figure 1.2 Map showing the nearly 30 million Ocean Biogeographic Information System (OBIS) records of 120,000 species. Colors represent data collected prior to the Census of Marine Life (in blue) and data collected during the program (yellow and red). This database provides global coverage with an average of one data point per every 12 km². The map also illustrates the broad areas of seafloor where no samples have been collected (Ausubel et al., 2010).

The underlying tenet of potential habitat mapping is that mapping the spatial distribution of habitats provides a means of estimating the occurrence of biota which commonly utilize that habitat type (Greene et al., 2007). From the perspective of management and conservation, if the potential habitats are protected then the biodiversity associated with those habitats will also be protected (at least to some extent). Furthermore, it follows that an area that supports a high diversity of habitats (high habitat heterogeneity) can be expected to support a greater biodiversity than an area which contains only a few (or one) habitat types; this is the so-called habitat heterogeneity hypothesis and it is a cornerstone of ecological theory (Tews et al., 2004).

Habitats are a shorthand way of describing and integrating other biophysical and ecosystem information. To nominate tropical coral reef habitat, temperate kelp forest habitat or abyssal seamount habitat (e.g.,) immediately specifies particular associated biota plus the accompanying environmental attributes. It follows that there is a clear role for using environmental attributes that we can map and which exert control over biodiversity. In other words, we study and map habitats and other surrogates for biodiversity and use these to design our marine environmental management measures. The objective for marine scientists tasked with conserving biodiversity is therefore to identify and make use of measurable attributes or indicators of biodiversity (e.g., Levinton, 2001). Understanding the different measurable environmental parameters that exert control over marine biodiversity underlies much of the content of this book.

Geomorphology and habitats

Among the physical attributes mapped and measured in detail in recent times using multibeam sonar equipment is the geomorphology of the seafloor. Temperate rocky reefs on the continental shelf, seamounts, submarine canyons, rocky ridges, pinnacles, ledges, escarpments, and muddy basins; these are examples of different geomorphic features that might each be expected to be associated with particular types of benthic habitat. The organization of this book (in terms of geomorphic features) is designed to advance our understanding of the different habitats associated with particular geomorphic features, and to allow examples to be compared and contrasted between different regions of the earth.

It might also be argued that the diversity of seabed geomorphic features has an intrinsic value of its own. The natural diversity of geological features has been termed geodiversity by some scientists, and the conservation of such diversity can be included as a criterion in making management decisions (Gray, 2004). This concept is not unfamiliar to conservationists, because many iconic terrestrial parks are defined on the basis of a prominent physical feature (e.g., the Grand Canyon and Mount Rainier in the United States or Uluru in Australia) and similarly some MPAs are defined by the presence of a particular reef, island, or rocky promontory. However, biological aspects of habitats are emphasized by most government agencies and nature conservation organizations and in many cases there is little if any acknowledgment of the geological aspects of habitats (Gray, 2004).

Habitat mapping technologies and approaches

The case studies in this book present examples of habitat maps that have been produced using a range of technologies, including satellite, airborne, and remotely operated drones. Multibeam swath sonar, sidescan sonar, ship-deployed remotely operated vehicles (ROVs), ship-deployed underwater cameras and videos, autonomous underwater vehicles (AUV), manned submersibles, and direct sampling of the seafloor are also commonly employed technologies (Table 1.2). A key point is that habitat mapping surveys will use several complementary technologies to map and sample the environment; determining the optimal combination of technologies to be deployed on a survey is a challenging task for habitat mapping scientists. The different systems have different applications for mapping different habitats at different spatial scales and the terminology may be confusing for some readers, which is why they are briefly reviewed here. In essence, seabed mapping technologies can be divided into four broad groups: (1) acoustic, sonar technology; (2) remote sensing based on natural or transmitted light; (3) underwater photography and video; and (4) direct sampling of sediment and biota.

Table 1.2

Note that most case studies employed multiple technologies; 35 studies used multibeam sonar at some frequency and 43 specified that some form of vessel-deployed camera or video system was used. Examples of technology listed here featured as a unique and major part of the case study.

Sonar systems

Measuring the water depth using acoustic (sonar) technology is based upon measuring the time taken for sound waves to travel between the vessel and the seafloor and back again. Transducers are the devices used to transmit and receive sound pulses from a vessel. The most advanced technology is called multibeam sonar that uses multiple (>100) sound beams to map the depth of water in a swath of the seabed across the track of the ship (Fig. 1.3), in contrast to a single-beam sonar which only maps a single row of points located directly below the ship. Modern multibeam systems are coupled with the Global Positioning System (GPS) to create accurate bathymetric maps (seabed topographic maps) that are presented in many of the case studies in this book. Different frequencies (measured in kilohertz; kHz) are used to map different water depths: higher frequencies (>100 kHz) are used in water depths of 10–100 m, frequencies of less than around 30 kHz are used in water depths 100–2000 m, and a frequency of around 12 kHz is used to map the abyssal depths of the ocean. Lower frequency (<30 kHz) systems utilize large (expensive) arrays of transducers that must be mounted on the hull of a ship, whereas higher frequency (>100 kHz) systems are smaller in size and can be deployed from smaller research vessels (often as portable systems). For different frequencies there is also a trade-off between area mapped and resolution: higher frequency, shallow water systems provide finer spatial resolution than lower frequency, deepwater systems, whereas lower frequency systems map larger areas of seabed in a single sweep of seafloor mapping compared with higher frequency systems (Table 1.2).

Figure 1.3 Multibeam sonar is used to map the depth of water in a swath across the ship’s track, allowing a map of the seafloor to be constructed. Source: Used with permission from the New Zealand Institute of Water and Atmospheric Sciences.

When the sound pulses bounce off the seafloor, the strength of the echo depends on the roughness and hardness of the seafloor; rougher and/or harder surfaces produce a stronger echo. Because of this, the strength of the sonar reflection (the backscatter) provides information on the seafloor topography and the presence of rock or sediment on the bottom. An older technology employing transducers located in a fish towed behind the survey vessel is known as sidescan sonar and it collects only acoustic backscatter data. Sidescan sonars are still used mainly because the technology is easy to deploy from small vessels and is less expensive than multibeam sonar. The resolution of towed sidescan sonar systems can exceed that of multibeam systems, but the exact location of the towfish behind the vessel is difficult to measure. This means that the data cannot easily be accurately located, which introduces errors when the backscatter data are combined with existing bathymetric data. A significant advantage of multibeam sonar is that it generates both accurate (georeferenced) water depth and backscatter data simultaneously.

Continuous seismic reflection profiling (seismic profiling) is another acoustic method used in some case studies (Table 1.2). This method is based on a sound source which generates acoustic pulses generally of a low frequency (usually <3–4 kHz, depending on the source) and having much higher energy compared with conventional echo sounders. Some of the energy from a seismic acoustic pulse is reflected from the seafloor directly back to the ship (as in an echo sounder), but part of the energy is able to penetrate into the seabed and reflect back off different rock layers beneath the seafloor. In this way a single vertical profile, showing the thicknesses of different rock and sediment layers, is created as the vessel traverses an area.

Large (more powerful) seismic systems commonly use a separate sound source in which the sound pulses are generated by high-pressure air guns or electric sparkers or boomers, and the return signal is received by a second towed array of receivers (contained in a seismic eel). Smaller, less powerful subbottom profiler systems (basically large echo sounders) have transducers that send and receive the acoustic pulse from a single unit. Most modern research vessels have such subbottom profilers built in. Smaller portable systems can be towed behind, or deployed over the side of, smaller research vessels.

Remote sensing based on natural or transmitted light

Remotely sensed images of the shallow marine environment can be collected from satellites or aircraft to generate snapshots and time series of chlorophyll, ocean temperature (McClain, 2009), wave climate (Hemer et al., 2009), and a number of other properties (Dankers et al., 2011). Satellite passive sensors rely on natural solar radiation reflected from the surface of the earth. Systems deployed from aircraft can use natural light but also use active radar sensors or laser sources to create images and gather information.

Light imaging, detection, and ranging (LIDAR) technology utilizes the reflective and transmissive properties of water and the seafloor to measure water depth using a laser, usually deployed from an aircraft. When an airborne laser beam is aimed vertically at the sea surface, the infrared is reflected while the blue-green light is transmitted through the water column. The blue-green light reflects off the seafloor (in shallow water) and water depth is calculated from the time difference between the surface and bottom returns. LIDAR systems are useful for mapping shallow water areas, to a maximum depth of around 30 m (depending on the clarity of the water).

Underwater cameras

In order to map the occurrence of plants and animals on the seafloor, scientists collect underwater images using still and video cameras. Video data can be overlain on acoustic data, such as multibeam bathymetry and backscatter, to examine the relationships between seafloor depth, shape, composition, and plant and animal distributions. Directly observing the seafloor geology, plants, and animals not only allows for rapid characterization (Anderson et al., 2007) but it also provides the foundation to monitor future changes. Cameras can be lowered on a wire to the seabed, towed behind the vessel on a sled, deployed from submersibles, or mounted in ROVs and AUVs. In most ship-deployed systems the digital camera images are sent via a cable to a recorder and TV screen on the ship, allowing biota and habitats to be viewed and assessed in real time (Anderson et al., 2007). Multiple passes over an object on the seafloor (or viewed from multiple camera lenses mounted on an underwater vehicle) can be used to create digital 3D models of the object for study and analysis (see Chapter 13: Seabed habitats of the Bay of Fundy, Atlantic Canada, for example). Another use of cameras is to mount them with some kind of bait in the field of view to obtain insights into the mobile animals that inhabit a particular location that come to feed on the food provided (see Chapter 28: Temperate rocky reef on the southeast Australian continental shelf, Chapter 37: Substrate mapping to inform ecosystem science and marine spatial planning around the Main Hawaiian Islands, and Chapter 59: Geomorphology and benthic habitats of the Kermadec Trench, SW Pacific Ocean).

Seafloor sampling

In order to build our understanding of habitats, all imagery and mapping data must be correlated with samples obtained from the seabed. In particular, sediment properties (grain size, mineralogy, etc.) and the taxonomy of most species can only be accurately determined from physical samples. To lower on a wire some device to the seafloor in order to obtain a sediment sample or biological specimen involves technologies that have been developed since the Challenger expedition in 1872–76, and there are literally hundreds of different kinds of seafloor sampling devices in existence. Different devices have been used in many of the case studies presented in this book. Some good textbooks describing different marine geological and biological sampling methods and techniques are Seibold and Berger (1996), Ericson (2003), and Levinton (2001).

A drawback of these older seabed sampling technologies is that the samples are collected from random locations on the seabed—the spatial context of the biological specimen returned is poorly constrained. Using modern satellite navigation systems coupled with acoustic telemetry the location of sampling devices can now be accurately calculated, but even this technology has its limitations in depths of more than a few hundred meters. One alternative is to use manned submersibles or ROVs, which allow scientists to collect samples using a robotic arm, with the advantage that the samples are collected from known locations and in the context of the surrounding environment that can be imaged and measured at the same time as the samples are collected (see Chapter 37: Substrate mapping to inform ecosystem science and marine spatial planning around the Main Hawaiian Islands, or Chapter 54: Chemosynthetic seep communities triggered by seabed slumping off of northern Papua New Guinea, for example). The trade-off is that manned submersibles are expensive to build and operate and they can cover only small areas of seabed during each deployment (Table 1.2).

Acknowledgments

This chapter is updated from the version published in the 2012 volume with minor additions to references and text as needed. The authors acknowledge the financial assistance of UN Environment/GRID-Arendal.

References

1. Anderson TJ, Chochrane GR, Roberts DA, Chezar H, Hatcher G. A rapid method to characterise seabed habitats and associated macro-organisms. In: Greene G, Todd BJ, eds. Mapping the Seafloor for Habitat Characterisation. Geological Association of Canada 2007;75–83.

2. Ausubel JH, Crist DT, Waggoner PE, eds. First Census of Marine Life 2010: Highlights of a Decade of Discovery. Washington, DC: Census of Marine Life; 2010; http://www.coml.org/.

3. Connor DW, Allen JH, Golding N, et al. Marine Habitat Classification for Britain and Ireland Version 04.05 Peterborough: Joint Nature Conservation Committee; 2004.

4. Dankers N, van Duin W, Baptist M, Dijkman E, Cremer J. Ch 11: The Wadden Sea in the Netherlands: ecotopes in a World Heritage barrier island system. In: Harris PT, Baker EK, eds. Seafloor Geomorphology as Benthic Habitat: GeoHab Atlas of Seafloor Geomorphic Features and Benthic Habitats. Amsterdam: Elsevier; 2011.

5. Ericson J. Marine Geology: Exploring the New Frontiers of the Ocean New York: Facts on File; 2003.

6. Gray M. Geodiversity - Valuing and Conserving Abiotic Nature Chichester: John Wiley & Sons; 2004.

7. Greene HG, Bizzarro JJ, O’Connell VM, Brylinsky CK. Construction of digital potential benthic habitat maps using a coded classification scheme and its application. In: Todd BJ, Greene HG, eds. Mapping the Seafloor for Habitat Characterisation. St. Johns, Newfoundland: Geological Association of Canada Special Paper 47; 2007;141–156.

8. Hemer MA, Church JA, Hunter JR. Variability and trends in the directional wave climate of the Southern Hemisphere. Int J Climatol. 2009;30:475–491.

9. IOC-UNESCO, 2009. An assessment of assessments, findings of the group of experts. Start-Up Phase of a Regular Process for Global Reporting and Assessment of the State of the Marine Environment, Including Socio-economic Aspects. United Nations, UNEP and IOC-UNESCO, Valetta, Malta, p. 208.

10. Kenny AJ, Cato I, Desprez M, Fader G, Schüttenhelm RTE, Side J. An overview of seabed-mapping technologies in the context of marine habitat classification. ICES J Marine Sci. 2003;60:411–418.

11. Levinton JS. Marine Biology: Function, Biodiversity, Ecology New York: Oxford University Press; 2001.

12. McClain CR. A decade of satellite ocean color observations. Ann Rev Mar Sci. 2009;1:19–42.

13. Seibold E, Berger WH. The Sea Floor: An Introduction to Marine Geology Berlin: Springer-Verlag; 1996.

14. Tews J, Brose U, Grimm V, et al. Animal species diversity driven by habitat heterogeneity/diversity: the importance of keystone structures. J Biogeogr. 2004;31:79–92.

Chapter 2

Habitat mapping and marine management

Elaine K. Baker¹ and Peter T. Harris²,    ¹UNEP/GRID-Arendal, School of Geoscience, University of Sydney, Sydney, NSW, Australia,    ²UNEP/GRID-Arendal, Arendal, Norway

Abstract

Demands are being made of the marine environment that threaten to erode the natural, social, and economic benefits that human society derives from the oceans. Expanding populations ensure a continuing increase in the variety and complexity of marine-based activities—fishing, power generation, tourism, mineral extraction, shipping, etc.

The two most commonly acknowledged purposes for habitat mapping in the case studies contained in this book are to support government spatial marine planning, management, and decision-making and to support and underpin the design of marine protected areas (see Chapter 60: GeoHab Atlas of seafloor geomorphic features and benthic habitats–synthesis and lessons learned).

Keywords

Marine spatial planning; ecosystem based management; benthic habitat; fisheries management; marine-protected areas; marine environmental assessments

Marine habitat mapping: a tool for environmentally sound management of the ocean

Introduction

At present the majority of human activities are still localized within the EEZs of coastal states (e.g., 100% of oil and gas extraction, 100% of aggregate mining, and the majority of the global fish catch) and are therefore managed by local, regional, or national bodies under the governance of the sovereign state. There are often numerous organizations involved, each responsible for a sector, activity, or location. Analysis of the shortcomings of ocean policy often points to the limitations of the fragmented sectoral approach (Salomon and Dross, 2018) (e.g., shipping, fishing, oil and gas development). This governance approach may have been effective in the past when there was limited competition for resources, but fails to take into account the additional pressures in today’s world of diminishing resources and increasing environmental degradation. A more integrated policy framework that supports sustainable ocean management is required. However, implementing integrated ocean management is not easy, as there are significant economic (e.g., fishing subsidies) and social drivers (e.g., the lack of power, key institutional barriers) that continue to support sectoral division.

Transformative change in ocean management

The recently released Global Environmental Outlook assesses the state of the world’s oceans and coasts, focusing on three main areas—coral reefs, fishing, and marine litter (United Nations Environment Programme, Global Environment Outlook Report-6). While the report only looks at a subset of drivers and pressures (the 2016 World Ocean Assessment endeavored to assess a more complete selection; United Nations Convention on the Law of the Sea), the observation that transformative change is required is likely applicable to many other areas of use and management if we want a sustainable ocean.

The United Nations Convention on the Law of the Sea provides the legal framework for the protection and preservation of the marine environment. It contains a general obligation for States to protect and preserve the marine environment, both within and beyond national jurisdiction (article 192). For example, it requires States to consider the effects of fishing on species associated with targeted species, that is, to go beyond the consideration of a single species and to recognize the connectivity of elements comprising a functioning ecosystem.

However, while ecosystem-based management (EBM) is advocated in international agreements like these and by national and local authorities, it has often been problematic to translate into operational management (e.g., Young et al., 2007).

Marine habitat mapping to support sustainable ocean management

Cogan et al. (2009) examined the essential components of EBM in order to illustrate how marine habitat mapping can be incorporated into EBM and to help facilitate the adoption of this form of management. They note that one of the initial steps in EBM should be to characterize the habitat features of the ecosystem. Accurate descriptions of marine habitats are central to spatial marine management. As discussed in Chapter 1, Why map benthic habitats? (this volume), utilizing different techniques habitat mapping can be scaled to provide information on a single habitat (e.g., a hydrothermal vent) or expanded to national or international levels, such as a large marine ecosystem (e.g., the UNEP Transboundary Waters Assessment Programme which includes Large Marine Ecosystems (LMEs) as an assessment unit; UNEP, 2011). The important point is that EBM requires that the scale of governance is matched to the scale of the ecosystem and it is largely through marine mapping that ecological boundaries are defined. Spatial mismatches often occur when jurisdictional boundaries are too small for effective management (e.g., in cases where species forage or migrate across national boundaries; United Nations Convention on the Law of the Sea).

The drivers, pressures, state, impact response (DPSIR) framework (EEA, 1999; Fig. 2.1) is an effective way of illustrating the role of habitat mapping in deriving indicators to describe the state of the environment within the EBM context. The state (Fig. 2.1) is defined as the condition of the system at a specific time and is represented by a set of descriptors of system attributes that are affected by pressures. Examples of state descriptors could be sediment type, species composition, habitat structure, etc. The DPSIR framework relates large-scale drivers of change (e.g., trawling) to the pressures they exert (e.g., habitat loss) which cause changes in the state of the environment (e.g., an increase in the area of modified habitat) resulting in impacts on biodiversity and human well-being (e.g., loss of fisheries income), thereby leading to institutional responses, policy development, target setting (e.g., establishment of an marine protected area (MPA), or other zoning framework). The fundamental concept is that the species abundance and composition of any ecosystem is determined by the physical environment in combination with impacts from human management.

Figure 2.1 The DPSIR tool is used for organizing information about the state of the environment and describing interactions between society and environment. The figure illustrates where habitat mapping can fit into this process (i.e., assessment of the state of the habitat/ecosystem and predicting impacts). Source: Adapted from UNEP and IOC/UNESCO (2009).

Habitat mapping to support national, transboundary, and high seas marine management planning

Many national governments have adopted marine spatial planning (MSP) incorporating habitat mapping into the development of marine management plans. The Great Barrier Reef Marine Park is an often cited example of a successful multiuse marine environment where MSP has been applied. It is referred to as a place-based management system (Young et al., 2007; Douvere and Ehler, 2009), the key element of which is a zoning plan that defines what activities can occur in specific locations in order to protect the environment and to separate potentially conflicting activities. The zoning plan was updated in 2004 based on the results of investigations to determine the major habitat types of the Great Barrier Reef Region (GBRMPA, 2004). The new Zoning Plan aims to protect representative examples of each habitat type within a network of no-take or highly protected areas. Representative areas were determined from habitat maps compiled using all available biophysical, biological, and oceanographic datasets and surrogates developed to approximate different habitat types. This information was used to define 70 different habitat types or bioregions (30 reef bioregions and 40 nonreef bioregions) across the Great Barrier Reef. The Great Barrier Reef is an example of EBM and MSP, underpinned by comprehensive habitat mapping, that provides for conservation, tourism, fishing (including dredging and trawling), and other activities within a World Heritage area.

The Geological Survey of Canada Atlantic (GSCA) has been a pioneer in the development of habitat mapping as a tool for fish stock assessment, maximizing fishing efficiency, and sustainable ocean management (Kostylev et al., 2008). GSCA developed a habitat template that integrates data that can be associated with the life history traits of organisms. The approach is based on the theory that relates species life history traits to particular properties of the environment. In this case the template utilizes selective forces related to physical disturbance of the environment and scope for growth (related to food availability, temperature, temperature variability, and oxygen saturation). In contrast to many habitat mapping techniques, the template predicts which life history traits will be best suited to a particular physical location and not which organisms will live there (Kostylev and Hannah, 2007). In documenting the role of habitat mapping in managing the Canadian marine environment, major improvements to the Canadian scallop fishery, identification of sensitive sponge habitats for incorporation into MPAs on the Pacific Coast, and improved decision-making related to offshore infrastructure development are cited (Pickrill and Kostylev, 2007).

Transboundary marine habitat mapping initiatives have been developed to both provide an EBM approach to a shared marine environment and also to produce standardized MSP tools and templates for management planning and decision-making of shared resources (e.g., Noji et al., 2004; BALANCE, 2008; Robinson et al., 2011). The EU Marine Strategy Framework Directive (2008) requires member states to manage their seas to achieve or maintain Good Environmental Status (GES) by 2020. The GES assessment includes biological diversity and seafloor integrity, both of which will require habitat mapping to develop indicators and set quality targets.

Ardron et al. (2007), in their paper on MSP in the high seas, noted that while not explicitly specified in UNCLOS or the convention on biodiversity (CBD), MSP is a practical way for States to fulfill their obligations related to the protection and preservation of the marine environment. However due to the difficulty and expense of direct observation and biological sampling in the deep sea, there have been suggestions that more predicative modeling is required (Harris and Whiteway, 2009; ICES, 2010). Habitat mapping based on seafloor geomorphology is an alternative approach to defining benthic habitats in the absence of data. This information can be used as proxies for biological communities and species diversity (e.g., Hockey and Branch, 1997; Roff and Taylor, 2000; Banks and Skilleter, 2002; Roberts et al., 2003). A global seafloor geomorphology map such as published by Harris et al. (2014) provides spatial information on the potential distribution of ecosystems for management of the deep-sea region. Impacts to deep-sea habitats are mostly related to deep-sea trawling and disposal of marine debris (see Chapter 3: Anthropogenic threats to benthic habitats).

Benthic habitat mapping applications

Effective management requires decisions on what, where, and how much of a particular activity is sustainable and habitat maps are effective tools that provide science-based information to help make these decisions. The majority of case studies contained in this volume were funded by government organizations and carried out specifically to support industry or conservation management and decision-making.

Under the broad heading of MSP there are numerous specific examples of where benthic habitat mapping has been applied, including:

• Fisheries management

• Supporting the design of marine reserves

• Site selection and environmental impact of offshore development

• Dredge spoil disposal management

Habitat mapping and fisheries management

Poor fisheries management is one of the biggest threats to marine biodiversity and benthic habitats. It is universally recognized that many target species are overexploited and that impacts on target species impact the whole ecosystem and that these impacts are cumulative (United Nations Environment Programme, Global Environment Outlook Report-6; Worm et al., 2009). The World Summit on Sustainable Development called for the restoration of depleted fish stocks to maximum sustainable yields where possible by 2015 and the elimination of destructive fishing practices. In a recent analysis of fisheries management effectiveness across 209 EEZs it was found that only 5% scored in the top quarter of the defined effectiveness scale (Mora et al., 2009).

The adverse effects of fishing on the environment have been comprehensively reviewed (e.g., Dayton et al., 2002; see Chapter 3: Anthropogenic threats to benthic habitats), but in summary include a reduction in abundance of the target species, reduced spawning potential, and evolutionary changes such as smaller sizes, earlier maturity, and elevated reproductive effort; organisms associated with the target species are also affected, as bycatch or through changes in predator prey dynamics, competitive interactions, relative species abundance, and other ecological relationships (Garcia and Cochrane, 2005; Jorgensen et al., 2007 and references therein). Then there are also the impacts from habitat disturbance. Fishing practices can alter or destroy seabed habitats, which can lead to loss of species diversity, reduced populations, and spawning ability. The degree and severity of these adverse effects on biodiversity and the seabed depend on a variety of factors, including the spatial extent of fishing, the level of fishing effort and the fishing method used. Benthic habitat mapping can provide critical information relevant to these factors, which aids both environmental and economic sustainability.

In fact habitat mapping is part of the commitment to an ecosystem approach to fisheries (EAF) that has been gaining ground for the last decade or more (e.g., FAO, 2003). To implement EAF, managers need to make decisions based on an understanding of how these decisions will affect both the fishery and the ecosystem. Improving fisheries management was cited as the second most common reason (after conservation) for carrying out the studies in this volume (Chapter 60: GeoHab Atlas of seafloor geomorphic features and benthic habitats–synthesis and lessons learned). Habitat maps are, for example, compiled to assess a fishery resource, including determining areas of suitable or essential habitat of a particular species or life stage; to assess the vulnerability of seafloor features to fishing impacts; and to aid in the design of fisheries reserves. The ability to track and predict the spatial dynamics of fish using key environmental indicators like benthic habitat, may become increasingly important as climate change alters the geographical distribution patterns of many marine populations (Planque et al., 2010).

Many fish species depend on specific habitats to complete their life cycle, so identifying and protecting these essential habitats also benefits fisheries. The destructive impacts of some fishing methods, such as bottom trawls and dredges, on benthic habitats are widely acknowledged (e.g., NRC, 2002). There are numerous regulatory examples that focus on habitat protection. For example, the United States Sustainable Fisheries Act, requires fisheries managers to identify and describe essential fish habitat (EFH) and evaluate the effects of all fishing practices on seafloor habitat.

Assessment of fishery resources

Fisheries management has in the past relied on stock assessment models to set catch allowances or maximum sustainable yields, which do not include habitat data (Hart and Grabowski, 2009). In the traditional single-species stock assessment, catch, abundance, and life history data are used to construct models that are used to establish allowable harvest quotas (Copps et al., 2007). But as the ecosystem approach becomes an important part of management, determining catch levels and auditing the effectiveness of management needs to include managing the spatial distribution of effort and developing indicators to evaluate the effect of the fishery on target species, bycatch, and habitat features (Rice and Rivard, 2007). The EAF reverses the order of management priorities to start with the ecosystem rather than the target species and because it emphasizes habitat and ecosystem function, management models need to incorporate spatial structure and environmental processes (Pikitch et al., 2004).

Examples of the use of habitat mapping in stock assessment can be found in numerous studies and with improved mapping technology and data coverage habitat mapping is becoming more widely applied to fisheries management. For example, Kostylev et al. (2003) found links between scallop abundance, sediment type, and habitat structure that allowed multibeam backscatter data to be used to greatly improve stock abundance estimates of a scallop fishery on the Scotian Shelf. In southeast Alaska, yellow-eye rockfish stocks are estimated directly from habitat maps of rugged rocky seafloor terrain (O’Connell et al., 2007). Galparsoro et al. (2009) used seafloor morphological characteristics in the Bay of Biscay to predict the most suitable habitat characteristics for the European lobster. A similar study was carried out to predict rockfish distribution on Cordell Bank, California (Young et al., 2007). These various habitat mapping applications, that accurately characterize seabed habitats, can be used to maximize fishing effort, making it more cost-effective by locating the habitat where the resource is more likely to be found. This also has the added benefit of limiting environmental damage as habitats where the resource is less likely to be found can be avoided.

A workshop on integrating seafloor mapping and benthic ecology into fisheries management in the Gulf of Maine (Hart and Grabowski, 2009) reported that future stock assessments needed to include EFH information that identified habitats where spawning, growth, and survival are high. To understand ecosystem dynamics in order to maximize productivity, fisheries managers need to know what habitat features support increased productivity, where they are located, and how they are affected by different kinds of human-induced (e.g., trawling) and natural disturbance.

Assessing the vulnerability of ecosystems to fishing impacts

Identifying areas that are vulnerable to fishing impacts has been important in the conservation efforts behind the delineation of MPAs or no-catch zones. Criteria for identifying vulnerable marine ecosystems (VMEs) include uniqueness or rarity of species or habitats, functional significance of the habitat, fragility, and ecosystems that are structurally complex or have life history traits that hinder the chance of recovery (e.g., slow growth rates, late maturity, etc.). VMEs are generally associated with specific undersea morphology, including topographically abrupt features, the summits and flanks of seamounts, submarine canyons, hydrothermal vents, and cold seeps (Auster et al., 2010). For this reason habitat mapping is an effective tool in identifying and predicting the location of VMEs. There is a continuum between EFH and VMEs—both require protection and when taking an ecosystem management approach similar concerns exist.

Fishing affects marine habitats and ecosystems in a number of ways depending on the type of fishing gear employed and the spatial and temporal extent of fishing. Trawls and dredges are traditionally dragged across the seabed to catch demersal fish, some semipelagic species, and shellfish. This method of fishing modifies the seabed habitat; some trawls act like plows that can turn over the top 30 cm of sediment (Caddy, 1973). In disturbing the structure of the seafloor, towed fishing gear changes the composition of the biological community and disrupts the food web (NRC, 2002).

In 2005 the General Fisheries Commission for the Mediterranean banned the use of any towed fishing gear below 1000 m, which equates to approximately 58% of the Mediterranean basin. This area contains ecosystems associated with distinctive benthic habitats such as mud volcanoes and thermal vents (Dando et al., 1999), which are associated with high biodiversity and are also vulnerable to structural damage.

Seamounts have been identified as areas of enhanced biodiversity and productivity compared to the surrounding ocean. The occurrence of hard substrate provides for habitat building organisms such as corals and sponges. Seamounts are known as aggregating locations for tuna, and as a consequence, many are heavily exploited by fisheries. A recent study examining the association between long-line tuna catch and seamounts identified higher catch rates associated with some seamounts in the Pacific Ocean (Morato et al., 2010). If we can clarify the relationship between seamounts and tuna this kind of information can have significant management applications related to both fishing effort and conservation of these VMEs. The authors suggest that to understand the factors driving tuna aggregation on specific seamounts, habitat mapping incorporating both detailed oceanographic and improved seamount morphological data is required.

Mapping techniques can be used in environmental monitoring—comparing the habitat structure and ecosystem between fished and unfished areas and monitoring recovery rates of degraded systems. For example, sessile fauna that are particularly vulnerable to damage from trawling, like the deepwater corals that form structural habitats on the tops and upper sides of seamounts, can be identified by their acoustic signature (Robinson et al., 2011). Similarly seabed disturbance mapping, based on trawl marks, is one component of habitat vulnerability analyses that can be used to select management areas (Hart and Grabowski, 2009).

Habitat mapping and the design of marine reserves (marine protected areas)

Declaring marine protected areas is a priority for nations

Given the perilous state of many marine species, a particularly urgent question is what can be done to conserve the diversity of life in the oceans? In answering that question the global consensus clearly and specifically highlights the need for nations to proclaim sanctuaries, or protected areas, for marine life within their marine jurisdictions. The United Nations CBD has set a global target of placing 10% of the oceans into MPAs by the year 2020 which has been endorsed by a large majority of the international community (www.seaaroundus.org).

A MPA is defined by the IUCN as any area of intertidal or subtidal terrain, together with its overlying water and associated flora, fauna, historical and cultural features, which has been reserved by law or other effective means to protect part or all of the enclosed environment (Gubbay, 1995). MPAs are therefore a spatial management tool, as opposed to regulations or laws which prohibit or limit specific activities like fishing for a certain species during certain periods. As summarized by Zacharias and Roff (2000), past efforts in protecting marine environments have focused on the conservation of species but, over the past 20 years, this has been supplemented by the conservation of spaces (MPAs).

In the establishment of MPAs managers often focus on ecological areas that are well understood by the public, such as coral reefs or seagrass beds. Value judgments are made about the importance of protecting some areas, but the development of a representative system of MPAs requires that all habitats are considered. Although conservation has been the main driver for the establishment of MPAs, they are also being delineated for the benefit of fisheries. MPAs are an important component of EBM (Halpern et al., 2010) and habitat mapping plays a major role by providing a spatial context for understanding ecosystems and dependent benthic species and communities.

How does habitat mapping assist in design of marine protected areas?

Although it is possible to use mainly biological information to select MPAs in the case of some small areas, such as in restricted coastal or coral reef settings, where there is sufficient biological information available (Edgar et al., 1997; Gladstone, 2002), in many cases particularly within large planning bioregions the necessary biological data sets on species distributions simply do not exist at the spatial scales that are needed to design MPAs. In such cases a number of workers advocate supplementing biological information with abiotic (i.e., geologic and oceanographic) indicators of benthic habitats and ecosystems as proxies for biological communities and species diversity (Hockey and Branch, 1997; Roff and Taylor, 2000; Banks and Skilleter, 2002; Roberts et al., 2003; Harris and Whiteway, 2009). In studies such as these the application of spatially more complete, abiotic information has been employed to systematically map different habitats to support MPA design. Indeed Greene et al. (1999) have devised a benthic marine habitat classification scheme that is strongly dependent upon seabed geology, whilst in Canada Roff and Taylor (2000) and Zacharias and Roff (2000) used primarily bottom physiography and oceanographic information in their hierarchical geophysical approach to classify and map marine environments.

From a precautionary perspective it is more valid to use the available information to identify and protect all of the physical variability that occurs between different habitats in an area that may or may not host a particular species or community, than it is to attempt to map actual biodiversity using species richness or assemblages. As stated by Day and Roff (2000) to best conserve biodiversity, we should be identifying and conserving representative spaces in conjunction with preserving individual species. If we can identify the appropriate representative spaces to be protected, then these will contain species we wish to conserve, as well as a suite of factors necessary for the health of those species, such as habitat and community structure.

The combination of physical variables that define different habitats can be mapped if we know what variables to measure and over what spatial–temporal scales to map and measure them. The point is that communities will always exploit the availability of any given habitat, and although the species comprising that community will vary depending on biological factors (e.g., predator–prey relationships), the overall community types (as opposed to communities of specific species) are recognizable. Different species occupy the same ecological niche in different occurrences of the same habitat (Day and Roff, 2000).

This has been called a potential habitats (Greene et al., 2007) mapping approach and it is comparable to the geophysical approach advocated by Day and Roff (2000), Zacharias and Roff (2000), and Roff et al. (2003). In this approach biological data are used to inform what physical parameters are most important for habitat characterization, or are the best surrogates for mapping habitats (e.g., using a probability distribution function), rather than attempting to directly map the diversity of species or communities. This is clearly a sensible approach for mapping biodiversity when one is dealing with large areas (e.g., at the scale of continental margins), but even for smaller areas geophysical information should be included along with biological data to assist with the identification of different habitats.

A good example of this approach is the recent study of Clark et al. (2011) on the distribution of deep-sea stony coral communities associated with seamounts, which are potentially threatened by deep benthic trawl fishing. The actual distribution of deep-sea stony coral communities is unknown. In order to estimate the potential distribution of stony corals Clark et al. (2011) used surrogates including known depth range, bottom water temperature, and seamount occurrence (i.e., the potential habitat) to predict stony coral distribution in the South Pacific Ocean. This information can then be used by managers to design MPAs and put in place conservation measures to protect them, even without a map of known coral distribution.

The part that habitat mapping has to play in MPA design involves such things as identifying critical habitat for threatened, endangered, or protected species (TEPS), mapping the location of known biodiversity hotspots or iconic features (Fig. 2.2), and identifying measurable ecological indicators that can be used to gauge the MPA’s performance. Biophysical information may be relevant to helping to identify iconic features such as submarine valleys, seamounts, or reef habitats, but a major role also arises for spatial information in understanding ecosystem processes and the distribution of representative habitats (Fig. 2.2).

Figure 2.2 Four different ways that an MPA might be designed: identifying threatened, endangered, or protected species (TEPS); critical TEPS habitat; the location of known biodiversity hotspots; or iconic features (from Harris, P.T., Heap, A.D., Whiteway, T., Post, A.L., 2008. Application of biophysical information to support Australia’s representative marine protected area program. Ocean Coastal Manage. 51, 701–711). Habitat information may be relevant to helping to identify iconic features such as submarine valleys, seamounts, or reef habitats, but a major role arises for spatial information in understanding ecosystem processes and the distribution of representative habitats.

Principles applied by many countries specify that MPAs must be comprehensive, adequate, and representative (e.g., UNEP/WCMC, 2008). In applying these principles to the design of a national MPA network, comprehensive means that MPAs must contain the full range of biodiversity, measured at an appropriate scale (habitat, ecosystem, species, or genetic) that occurs in the region of interest. These will include unique biological communities or habitats, but only as one part of the full spectrum of biodiversity that occurs in an area. The MPA network will be adequate if it contains a large enough area, with sufficiently redundant representation of different habitats, and it is protected to a large enough extent (if not a fully-protected MPA), that the ecosystems it contains will remain viable. Adequate replication of ecosystems is considered to be