Australian and New Zealand Environment and Conservation Council and Biological Diversity Advisory Committee
Commonwealth of Australia, 2001
ISBN 0 6425 4742 4
B. How does our biodiversity function?
Environmental processes, such as the water cycle, have been taught to school children in urban and rural areas for decades. Despite this, ecosystem processes were rarely considered by the public or policy makers until a problem such as soil erosion or invasion by prickly pear became obvious. The critical role of ecosystem processes as part of the complex biophysical environment was largely overlooked for two centuries as land was cleared for grazing and agriculture. One result has been that with reduced transpiration by trees and other deep-rooted vegetation, water tables have risen bringing dissolved salts to the surface and have caused the growing phenomenon of dryland salinity. We need an understanding of environmental processes so that we can anticipate the effects of human activity on ecosystems and choose to avoid or ameliorate environmental damage.
Ecosystem processes and function
Ecosystem processes include the interactions between predators and prey, herbivores and the plants they graze, and between competitors. They include many types of mutually beneficial interaction such as: pollination of flowering plants by insects and birds which obtain nectar; and nutrient uptake enhancing associations between mycorrhizal fungi and the roots of acacias, eucalypts and many other Australian native plants. Nitrogen fixation, by Rhizobium bacteria in the root nodules of legume plants 16, is an important ecosystem process in Australia's nitrogen poor soils. Decomposition and soil building are ecosystem processes. Finally, so fundamental that it is often overlooked, marine algae and terrestrial plants produce the oxygen that we breathe.
Ecosystem processes that produce a similar effect can be considered in functional terms. For instance, the function of the breakdown of organic matter and build up of fertile soil is carried out by several groups of organisms 17. These include bacteria which are particularly active decomposers in warm climates, fungi which are more dominant decomposers in cool climates and termites which consume woody litter and incorporate it into soils particularly in eastern and tropical Australia. Other examples of functional groups are the guilds of birds with similar feeding requirements. Further research is needed into functional groups and how these affect the distribution of particular species.
The interactions between biodiversity and the physical environment affect water quality, the water table level, nutrient cycling, soil fertility, soil retention, micro-climates, atmospheric circulation, marine currents and other global climate patterns. Nutrients move between the physical and biological spheres as they are taken up from the soil, water or atmosphere, pass through the food web (sometimes being concentrated), and are eventually released again with decomposition. Organic pollutants and heavy metals follow a similar cycle and may persist through many biophysical processes before being broken down or trapped in sediment. Considerable research is required into processes in soils and aquatic ecosystems – the research methodology itself needs to be tested for these ecosystems.
Changes in the biophysical carbon cycle have attracted much attention in recent years as a probable cause of global warming. Carbon is removed from the atmosphere by plants and bound in wood and is also removed by marine organisms and bound in calcium carbonate shells and skeletons. It is released again when wood is burnt or decomposed and when calcium carbonate is dissolved in ocean waters rather than being deposited as sediment. Atmospheric carbon contributes to greenhouse gases thought to be warming the planet and changing climate patterns.
Modelling and management decisions
Predictive modelling is needed to integrate information about different biophysical processes so that we can understand why species occur where they do and we can predict the effects of environmental change. For instance, BIOCLIM is used to predict places where a species could be expected to be found. It builds on the observed distribution of species and, for each observation point, the model uses the latitude, longitude, altitude, rainfall pattern and other climatic data. BIOCLIM is being used to predict changes in species distribution as a result of changes in the climate.
Research is needed to develop effective models of soil processes. Micro-organisms are critical to maintaining soil fertility and structure, and to help prevent soil acidification, compaction, erosion and salinisation. In temperate regions, there may be 20 000 kilograms of micro-organisms per hectare – as much or greater than the mass of most agricultural plants standing on the surface of that same area of land 18.
Conservation and multiple use areas need to be managed taking into account biophysical and ecosystem processes over the long term. Research is needed to understand where biodiversity can be removed to make space for agriculture and other human activities and where it is critical to retain or restore biodiversity to maintain ecosystem processes needed in the land or marine area (see Section E).
Informed natural resource management decision-making requires a comprehensive analysis of the value of ecosystem services (see Section C). A prerequisite for this analysis is a good understanding of ecosystem processes and their part in the biophysical environment.
5. Identifying ecosystem processes
Comprehensively examine ecosystem processes across a range of scales from micro-habitats to bioregions. Investigate the ecosystem function of key species.
Highest priority research
Undertake comprehensive research into ecosystem processes in selected areas such as:
- threatened habitats; and
- several entire catchments including the estuary and associated marine area.
Investigate the ecosystem function of critical species and groups where changes in their function may cause ecosystems to be threatened.
- For example, in key areas where changes in soil condition is causing loss of native biodiversity, investigate the function of soil organisms including how these organisms affect and are affected by: the biophysical soil environment, the distribution of plants and animals, and other ecosystem processes.
Research of national importance
- Identify and investigate ecosystem processes:
- in land, freshwater, estuarine and marine habitats;
- across a range of scales from micro-habitats to bioregions; involving interaction between species 19 and functional groups that affect their distribution;
- comprehensively, within single entire catchments including the estuary and associated marine area; and
- occurring across suites of catchments.
- Identify how key species and groups of species affect and are affected by other species, by physical and biophysical factors and by ecosystem processes. Note changes with natural events and threatening processes.
- Where studying functional groups of micro-organisms, determine what constitutes ecologically meaningful units, how these can be measured and the relationship between taxonomic and functional diversity.
To provide the basis for:
- predicting how threats and management practices will affect ecosystem processes;
- protecting and restoring ecosystem processes in threatened habitats;
- establishing a total economic value for ecosystem services, taking into account social and environmental benefits; and
- integrated natural resource management.
(1), (2) and (3) information on ecosystems, ecological communities and species
(4) make data and information accessible
(3) monitor changes in ecosystem processes
(12) assess risks from human activities and other threats
(13) develop predictive models
(15) develop educational materials.
Relevant policy commitments and legislation
National Strategy for the Conservation of Australia's Biological Diversity: Objective 1.1.2
Convention on Biological Diversity: Article 7(c)
Commonwealth Environment Protection and Biodiversity Conservation Act 1999: Sections 171
16. Nitrogen fixing legumes include acacias, clovers and related pasture plants, peas and many rotation crops used in agriculture such as lucerne.
17. References: Anderson JM 1988 and Lee KE 1983.
18. Reference: Saunders, D and Walker B 1998.
19. Species or other ecologically meaningful unit. Where a group of species share similar ecological functions, the group may constitute a more practical ecologically meaningful unit (EMU ) for study.