Indicators of Catchment Health: A Technical Perspective

By J Walker and DJ Reuter

The primary focus is to provide landholders, catchment groups, catchment and land protection boards, and rural communities with the best tools that science has so far developed for benchmarking and monitoring the condition of the land and water resources in the catchments. A diverse range of potential indicators has been reviewed and the most appropriate suite of indicators assembled to aid this focus. The proposed indicators cover farm productivity and financial performance, product quality, soil health, water quality and landscape integrity.

• Language: English
• Publisher: CSIRO PUBLISHING
• Release date: Jan 1, 1996
• ISBN: 9780643105751

Book preview

The Indicator Approach

1. Catchment health indicators: an overview

J. Walker  CSIRO Division of Water Resources, Canberra

D. Alexander  Office of Geographic Data Coordination, Melbourne

C. Irons  Centre for Resource and Environmental Science, Canberra

B. Jones  US EPA National Exposure Research Laboratory, Las Vegas USA

H. Penridge  Chiron Media, Mooloolah Qld

D. Rapport  University of Guelph, Ontario Canada

Highlights

A healthy catchment is one that can recover from perturbations. It is economically viable and environmentally self-sustaining.

Landholders wanting to adopt sustainable land use practices need simple ways of assessing the condition of their land and water resources.

Environmental indicators are short-hand descriptors of aspects of the environment.

Using indicator data that they have collected on their properties, landholders can compile report cards on the condition of their property i.e. on the state of the land and water relative to some desired state. They can also measure trends in their property’s condition i.e. changes over the time that they have been collecting data.

Data collected by landholders can, and should, be placed in a catchment context.

Improvements in catchment condition and trends will be detected when a critical mass of farmers in the catchment use indicator data to improve the condition of their land.

An indicator program designed to answer specific questions at the farm level has a better chance of success than a program that uses community-based data to address State and Federal issues.

While some standardisation of indicators and collection methods is advocated, tailoring this standard set to suit local issues and conditions is recommended.

An environmental indicator program could save tens of millions of dollars by better targeting Landcare expenditure and by stemming the current rate of land degradation.

Why Assess the Condition of Catchments?

Around the world there is concern about the capacity of natural resources to sustain human activities into the future. In our region, the impact of agricultural activity on natural resources was a major focus of attention for the Australian Government’s National Strategy for Ecologically Sustainable Development (Commonwealth of Australia 1992). Agricultural activities were found to be degrading biophysical resources on the land, and adding pollutants to streams and the atmosphere. It is crucial that ecologically sustainable practices be widely adopted.

The need is to be able to assess trends in land and water condition and do something before irreversible damage is done.

Data collected locally by landholders need to be placed in a catchment context.

Landholders need environmental health report cards to keep track of the biophysical properties and processes on their farms.

The Landcare and Total Catchment Management movements established in the late 1980s have done much to raise awareness of environmental issues in rural and urban areas. They have also encouraged adoption of practices that are economically attractive and ecologically sustainable.

But will sustainable practices be adopted widely, given that short term economic survival remains a critical concern of all landholders? Farmers will only invest in change when they see that their investment will improve their economic future. This decision will depend upon their making a reliable assessment of the status of their resource base.

The assessment must take account of more than the farm. Rising regional watertables caused by widespread tree clearing is just one example of on-farm activities affecting off-farm processes. Hence, techniques for assessing each landholder’s resource base must be able to be applied at both paddock and catchment scales.

Keeping Track: the Need for a Health Report Card

One obstacle to sustainable farming has been the lack of simple methods to assess the relative environmental condition of a farm within a catchment context.

Farmers compile production records and product prices to keep track of financial trends. In effect, they are compiling financial report cards for their farms that can be compared with others in their district. In the same way, landholders need environmental health report cards to keep track of the biophysical properties and processes on their farms.

Within a specific catchment, an environmental health report card offers a means of benchmarking, monitoring and evaluating trends in environmental properties and processes. Once a farm is assessed, longer term plans and staged remedial action can be implemented to improve productivity, profitability and environmental quality.

Unlike financial records that are relatively simple to compile, the environmental health report card needs to bring together data from several sources.

Biophysical processes are known to operate at a range of spatial scales (e.g. patch, paddock, farm, small catchment, large catchment and basin scales). They also operate at a range of temporal scales (e.g. paddocks need day to day management, but a catchment may take decades to show watertable changes). For management actions to be effective, planners require knowledge at the scales likely to influence these processes.

For example, salinisation at the patch scale can be caused by local features (e.g. a dyke, geological break, change in soil type, change in slope) or more substantial regional features (e.g. increased groundwater pressure caused by tree clearing). Only if wider-scale data are collected, can a wider-scale cause be detected and tackled. Response times to particular activities will also be different at different scales.

It follows that farm scale information on the environmental health report card needs to be amplified with data from a wider context. Using the catchment unit to give a spatial context to farm unit data has several advantages. The catchment unit offers an appropriate scale for many societal values (profitability, quality of life, recreation, aesthetics and so on) to link with landscape and ecosystem processes. It also links at a spatial scale with social and economic aspects which are usually in terms of a local government area (LGA).

These data are usually collected by State or Federal agencies or with assistance from local groups. Linkages between the data and information sources both at the same scale and at different scales are important.

Indicators to Assess Catchment Health

Just like any other type of report card, the environmental health report card will need to be based on a system of assessment. In the past, assessing changes in catchment condition has been left to various State and Federal bodies. Such sampling has rarely been spatially dense enough to provide detailed information to an individual landholder or community group. If communities want to use the information, community involvement in environmental monitoring is needed to fill in the gaps. Many communities are taking this approach (ANCA and CEPA 1994; Alexandra, Haffenden and White 1996) but the data collection is often time consuming and the data are not always appropriate to local issues.

Landholders and communities need a practical means of assessing condition and trends to address local issues. An environmental indicator program would offer this means.

Environmental indicators are conceptually similar to the economic indicators that appear in the daily newspapers. An indicator program based on a few carefully chosen indicators offers a rapid and cost-effective way of identifying trends in the condition of natural resources caused by farming.

In Australia and a variety of other countries, notably the United States, Canada, New Zealand and the Netherlands, schema have been proposed for monitoring and assessing environmental health. Some approaches have been developed to address national scale issues (e.g. DEST 1996; Davies 1994; SCARM 1993), whilst others focus on State issues (State of Environment reports (SoER) for all Australian States and Territories), local government area issues (Unisearch Research Services 1994) or local/site issues (e.g. Waterwatch). This wealth of experience can be used to identify which approaches and indicators are likely to be successful for any given purpose.

Who are the Intended Users of Catchment Health Indicators?

Presently in Australia there are many groups developing environmental or health indicators for a variety of purposes. In Figure 1-1, some of these groups are placed into spatial scales from national to farm. The questions addressed and the approaches adopted are different at the different scales. Further, the indicators needed to address the questions posed are likely to be different at the different scales.

One could suspect that few indicators will apply at all scales, but if these could be identified, they would be especially useful. Therefore, the first step in developing a report card is to involve user groups in defining the issues and aims. The user group that we are targeting are individual landholders, Landcare groups, total catchment management groups and regional catchment or land protection groups. These users are all likely to require indicators that can identify the nature and location of problems in order to begin remedial actions.

The purpose of this text is to outline the scientific basis for indicators and to suggest, from a long list of possibilities, a minimum set of indicators needed to define catchment condition and to assess trends. It documents the technical background against which individuals or groups can develop their own set of indicators to address the issues of their local area.

The approach is bottom-up. If individuals do not actively take part in the selection of indicators useful to them, and see some tangible benefits in collecting the data, then widespread adoption is unlikely. There is no suggestion that individual indicators can be aggregated to give a national picture; the use is at the self-help local level.

To go from this text to data collection requires feedback from community groups. More information needs to be gathered on spatial and temporal sampling and interpretation. These steps are planned.

Environmental indicators are conceptually similar to economic indicators.

Users are Landcare groups and land protection groups.

Individuals or groups can use this document as the technical background to develop their own set of indicators.

Figure 1-1 Environmental indicator programs operating at different scales around Australia

What are Environmental Health Indicators?

Definitions

Indicators are ‘measurable attributes of the environment that can be monitored via field observation, field sampling, remote sensing, or compilation of existing data’ (Meyer et al. 1992). A similar definition comes from SCARM (1993): ‘a composite set of attributes or measures which embody a particular aspect of the component of interest’. Indicators serve as shorthand descriptions of aspects of an environment. Indicators are selected from a wide range of possible attributes and can be used singly or in combination to assess the condition of the environment. Selection and use are described later in the text.

Ideally, each indicator is precise and accurate in describing a particular function of the environment and will serve to signal desirable or undesirable changes that have occurred, or may occur in the future (Landres 1992). Indicators are not intended as a complete set of parameters or variables that can be used in a process-based model. Rather, they are key attributes that give an impression of major trends and condition, and are based on the key components of the whole agro-ecosystem.

Kinds of Environmental Indicators

Researchers have categorised indicators in various ways. For example, Cairns and McCormick (1992) identify three types of indicators:

compliance indicators which assess deviations from previously defined conditions or acceptable limits

diagnostic indicators which identify the cause of deviation from acceptable limits

early warning indicators which signal an impending decline of conditions

Jenkins and Sanders (1992) converts the first two of these categories into three tiers of specificity:

tier 1 indicators: Is there a problem?

tier 2 indicators: What sort of problem is it?

tier 3 indicators: What is the specific cause of the problem?

Jenkins and Sanders follow a medical metaphor. From a preliminary examination, the patient (catchment) is judged to be sick or well. Then follows diagnosis of the nature of any illness, and finally the cure. In environmental applications, the condition of the system is assessed, trends in condition are evaluated, and causes are identified using a variety of techniques including indicators.

Different kinds of indicators find answers for different kinds of questions, at different scales and at different levels of complexity. It is vital to tailor the suite of indicators to answer the question being addressed by the user group. A standard set of indicators to suit a range of purposes is unlikely to be developed.

The Kinds of Indicators Needed to Assess Catchment Health

The indicators we consider to be the most useful for assessing catchment health are compliance indicators. Two types of compliance indicators are recognised:

condition indicators which define the state of the system relative to a desired state

trend indicators which measure how the system is changing

Because it is necessary to consider information at both the point (paddock) scale and the catchment scale, we further sub-divide the condition and trend indicators:

on-farm indicators which are mainly soil health attributes (e.g. pH, where several values are obtained per paddock)

These indicators are suitable for mapping the spatial distribution of values. In many cases (e.g. pH) average values have little meaning at an aggregated scale.

catchment indicators which are attributes that integrate whole catchment responses (e.g. changes in stream electrical conductivity, total area planted to trees)

These indicators give an overall response or inferred response, but do not indicate the location of ‘hot-spots’.

On-farm indicators give point values and are suitable for mapping the spatial distribution of values. Catchment indicators integrate whole catchment responses but do not indicate hot spot locations.

Condition indicators define the state of the system relative to a desired state. Trend indicators measure how the system is changing.

A few key attributes can give an impression of major trends and condition.

To encourage adoption, it is important that only the best indicators be chosen and that the set of indicators be kept as small as possible.

Terminology

Catchment health is the prime issue of interest. Many components contribute to catchment health and many attributes can be selected to address each component of the issue. Indicators measure these attributes.

Later in this chapter, we argue that the health of a catchment should be defined in terms of economic viability and self-sustaining delivery of goods and services. The prime concern of a farming community is to preserve the productivity and profitability of farmlands.

Productivity has therefore been chosen here as the first component of dryland farming catchments. Productivity is a measure of the condition of the system, but is considered here more as the basis of economic returns.

Economic returns (apart from fluctuations in commodity prices) are also in part determined by product quality. Product quality is used as the second component.

Productivity depends on a third component, local soil quality, which in turn may be impacted upon by farming practices. Off-site impacts of land use can be detected by measuring attributes of the water quality component.

The final component, landscape integrity, is a catchment scale component.

Each of these components can be described in terms of many attributes. These attributes can be measured using appropriate indicators. For example, one attribute of the fourth component, water quality, is the ability of streams to support aquatic life. An indicator that gives a reliable measure of this ability is the number of different macro-invertebrates found in the stream. By measuring macro-invertebrate diversity, landholders can gain information that contributes to their understanding of the biophysical processes of their stream, their farm and their catchment.

Providing indicators are chosen that reliably reflect the state of the corresponding components, the suite of indicators, when taken together, can provide a picture of the health status of the catchment as a whole.

How Many Indicators are Needed to Assess Catchment Health?

To encourage adoption, it is important that only indicators that meet the needs of the user group (e.g. reliability, reproducibility, interpretability, cheapness) are chosen. The final set should also include no more indicators than necessary. In Section Two, we recognise a minimum set of 29 indicators: 10 condition indicators, 10 trend indicators and 9 indicators of productivity, financial performance and product quality. This set is deemed sufficient to assess catchment health.

This minimum set can be expected to change depending on the issues addressed and the region (tropical, temperate etc.). However, the set will always remain small compared with the numbers of indicators in many other programs, e.g. Australian Bureau of Statistics (ABS) environmental data, State of Environment Reporting (SoER) or sustainability issues (e.g. sustainability of agriculture). ABS and SoER cover a wide range of issues and use a strict sampling procedure. The indicators they use address questions that have answers in the form of raw statistics from which no causal relationships are inferred. Nevertheless, the values may be compared with desired values and further work or policies initiated to improve particularly poor values.

Examples of the sorts of questions answered by these programs include:

What is the whale population in Australian waters?

What is the area of rainforest in Australia?

How much solid fuel is used in Australia?

One can expect to have many indicators in SoER, running into hundreds. Sustainability issues are deemed to be somewhere between SoER statistics and environmental health assessments in terms of numbers of indicators used. An example is the National Agricultural Sustainability Project (SCARM 1993). Although not finally decided, one can anticipate some 20-30 indicators, again based on aggregated data. To interpret these indicators will require much stricter sampling and quality assurance tests than is envisaged for a minimum set of catchment health indicators.

Interpretation Difficulties

Each indicator in the minimum set gives a window view of catchment health. As a suite they can be inspected for overall trends and evaluated against desired standards. No formal method is proposed to evaluate the suite of indicators.

Interpretation of environmental indicators requires a degree of judgement. Unlike economic indicators which have the dollar as a common unit, environmental measures do not have a common unit of measurement. In addition, the behaviour of many indicators over time is not known and threshold limits may vary from region to region. The latter point is important when examining the range of values in the tables in Section Two.

It is tempting to deal with these problems by developing so-called composite indicators (for example adding together ratings for several indicators). Alternatively we could develop a single aggregated index based again on some form of summation of several or many indicators. Neither of these approaches is recommended. Bulking indicators together in simple or sophisticated ways results in information loss. Error result from inappropriate weightings given to individual indicators and unknown interactions which occur between indicators. These methods will cause serious interpretation problems.

Even when the indicator values are considered separately, misinterpretation is possible. Indicators offer a simplified means of measuring complex environmental responses to farming practices. It is easy to mix up symptoms with causes, to assign a single cause when many factors interact, to infer large scale changes from a point measurement or to make incorrect inferences from a single sample taken in a fluctuating system. The strategy we adopted was to select indicators that were clearly linked to causes. We felt these were less likely to be misinterpreted.

Mapping on-farm indicators, and placing each indicator in a category from excellent to degraded, is the simplest and most useful way to interpret indicators. Thresholds for each indicator can be determined from field data at a regional scale.

The Concept