Biodiversity Theme Report
Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Dr Jann Williams, RMIT University, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06749 3
Increase in the Knowledge of Biodiversity (continued)
Number of research programs into the role of biodiversity in ecological processes [BD Indicator 24.5]
There have been no ARC Large Research Grants into the role of biodiversity in ecological processes in the last five years.
Number of research programs into surrogates [BD Indicator 24.4]
In the context of State of Environment reporting, and for biodiversity management in general, 'surrogates' measure the spatial distribution of biodiversity. They are distinct from indicators that measure the response of ecosystems to disturbance, and from umbrella species and flagship species that provide de facto protection for species that occupy the same habitat.
The taxon-based biodiversity surrogates approach targets resource management or landscape restoration efforts at a group of species and assumes that the needs of other taxa will be met (see Taxon-based biodiversity surrogates).
A simple strategy is to conserve areas that incorporate a range of environmental factors (Faith & Walker 1993). Environmental domains are geographical regions that enclose a continuous range of physical environmental parameters that are expected to be important in determining the distributions of species.
Vegetation maps are perhaps the most frequently used biodiversity surrogates. Much of the vegetation of the Australian continent has been classified and mapped (Commonwealth of Australia 1990; Specht et al. 1995). It is assumed that protection of a proportion of each vegetation type will protect sufficient proportions of the populations of other organisms. Vegetation maps may fail as surrogates in cases where sets of species are dependent on particular successional stages within a vegetation community (e.g. the old growth stage of a particular type of forest), or when species respond to environmental variables to which the vascular flora are insensitive.
No ARC Large Research Grants have been awarded on the subject of surrogates between 1995 and 2000.
Types 1, 2 and 4 have been proposed as indicators of biodiversity and types 3, 5, 6 and 7 as indicators of abiotic conditions and/or changes in ecological processes.Taxon-based biodiversity surrogate schemes have wide appeal because it is simply impossible to measure, monitor and manage all of biodiversity (Burgman & Lindenmayer 1998). The fundamental assumption of all taxon-based surrogate schemes is that if resource management or landscape restoration efforts are targeted at a group of species, the needs of other taxa will be provided. However, as early as the 1980s, several workers raised concerns about the conceptual, theoretical and practical basis for taxon-based surrogate schemes (e.g. Landres et al. 1988). None of these concerns have been adequately answered in the intervening years (Lindenmayer et al. 2000). Some of the many problems which afflict taxon-based surrogate schemes are outlined below.The effects of human perturbation such as landscape change and habitat fragmentation varies for each species and also between groups of species. Hence, the response of a given species or suite of species to landscape modification may reveal very little about the response of many other species in the same or different assemblage or group.Any species that is the specific target for conservation by particular management actions can no longer be an independent yardstick of those actions and, in turn, be regarded as a suitable surrogate for other taxa.There are problems stemming simply from choosing the wrong biodiversity surrogate that can arise from a lack of understanding of the causal relationship between the response of that species and the ecosystem conditions for which it is supposed to be indicate. There are also problems stemming simply from choosing the wrong indicator species. The case of the Bivalve Mollusc (Velesunio ambiguus) in Australian river systems is a classic example. Early research suggested that the species was an indicator of the presence of heavy metals (Walker 1981). Subsequent work found that the uptake of heavy metals by Velesunio ambiguusdid not reflect the extent of pollution in the surrounding riverine system, making the mollusc an unreliable, and thus entirely unsuitable, indicator species (Millington & Walker 1983). Robust causal relationships between surrogates and other elements of biodiversity have never been demonstrated (Lindenmayer et al. 2000).A recent study of surrogate schemes by Andelman and Fagan (2000) examined the efficacy of an array of types of taxon-based surrogate schemes including indicator species, flagship species and umbrella species. Andelman and Fagan (2000) found that none of the surrogate schemes captured more species or better protected habitat than a given species selected at random from the large databases they assembled to conduct their tests.Thus, a key problem with taxon-based surrogate schemes is that when a landscape is managed or restored in an attempt to meet the requirements of a given suite of species such as birds (e.g. through the focal species approach) it may be inappropriate to automatically assume that the food, shelter and breeding requirements of other plants and animals in the landscape have also been met.The inherent problems associated with the use of indicator species and other biodiversity surrogate schemes means that other approaches may be needed to conserve biodiversity as part of ecologically sustainable natural resource management. In the case of forest landscapes, Lindenmayer et al. (2000) recommended the adoption of what they termed 'structure-based' indicators. These included stand and landscape (spatial) level features of forests such as stand structural complexity and plant species composition, connectivity and heterogeneity. In addition to these structure-based indicators, Lindenmayer et al. (2000) advocated the following four key approaches to enhance biodiversity conservation in forests:
- the establishment of biodiversity priority areas (e.g. reserves) managed primarily for the conservation of biodiversity
- within production forests, the application of structure-based indicators, including structural complexity, connectivity and heterogeneity
- the deployment of a risk-spreading approach in wood production forests using multiple conservation strategies at multiple spatial scales
- the adoption of an adaptive management approach to test the validity of structure-based indices of biodiversity by treating management practices as experiments.
Taxon-based biodiversity surrogates schemes have been used widely in conservation management efforts in many parts of the world. The search for indicators of biodiversity has tended to focus on biological entities (e.g. gene frequencies, populations, species, species assemblages and communities) that might function as surrogates or proxies for other forms of biodiversity and/or reflect changes in ecosystem patterns or processes (Burgman & Lindenmayer 1998). Many types of biodiversity surrogate schemes have been proposed. Some of these include: indicator species, management indicator species, keystone species, umbrella species, and the focal species approach (Lindenmayer et al. 2000). The biodiversity surrogate scheme that has received greatest attention has been 'indicator species'.
The term indicator species has been used to mean many different things. Some examples of types of indicator species include:
- a species whose presence indicates the presence of a set of other species and whose absence indicates the lack of that entire set of species
- a keystone species, sensu Terborgh (1986), which is a species whose addition to, or loss from, an ecosystem leads to major changes in abundance or occurrence of at least one other species (e.g. Mills et al. 1993)
- a species whose presence indicates human-created abiotic conditions such as air or water pollution (often termed a pollution indicator species, Spellerberg 1994)
- a dominant species in the sense that it provides much of the biomass or number of individuals in an area
- a species that indicates particular environmental conditions like certain soil or rock types (Klinka et al. 1989)
- a species thought likely to be sensitive to, and to therefore serve as an early warning indicator of, environmental changes like global warming (Parsons 1991) or modified fire regimes (Wolseley & Aguirre-Hudson 1991) (sometimes termed a bioindicator species)
- a management indicator species, which is a species believed to reflect the effects of a disturbance regime or the efficacy of efforts to mitigate disturbance effects (Milledge et al. 1991).
Source: David Lindenmayer, Australian National University.
Proportion of bioregions covered by biological surveys [BD Indicator 14]
The data on this indicator are not readily available at a national or regional level, even for areas with relatively comprehensive survey records such as north-east New South Wales.