Forestry, fishery and farm managers must adopt flexible approach to ecosystems

The model, which was drawn up as part of research for a paper published in Conservation Ecology journal, was designed by researchers at University of Wisconsin-Madison to simulate a system of shallow lakes accumulating phosphorus runoff from upstream farms.

The runoff triggers eutrophication – the suffocation of aquatic life by algal blooms.

The farm-lake system is not only dependent on natural processes such as nutrient cycling and climate, but is also driven by human decisions based on farm economics and the costs of lake clean-up. This complexity is typical of the situations faced by all resource managers, from park rangers to the overseers of marine fisheries.

In order to put together a realistic simulation, the researchers began with the best available field data on the causes and consequences of phosphorus loading in lakes. Then they incorporated cost-benefit analysis (CBA), social theory, and a cast of characters, each with their own attitude toward resource management, buyers and sellers of information, governing boards, environmentalists, market managers and economists.

The goal for anyone ‘playing’ the programme is to sustain agricultural production without letting the lakes crash into eutrophication. The researchers were surprised by the results. Regardless of the player’s agenda or approach, the phosphorus dynamics of the lakes would invariably cause an algal bloom. Even ‘omniscient’ characters who were told exactly how the system functioned could not avoid an occasional phosphorus spike.

In most cases, the eutrophication is reversible, but it is a costly problem to fix, requiring drastic reductions in fertiliser use and corresponding losses in agricultural production.

The researchers attribute the crashes to the fact that every action affects a complex range of variables. The variables change at different speeds, some quickly (fertiliser inputs, crop prices), some slowly (phosphorus in the soil), so the net result of any action is very difficult to predict.

“The simulations use well-known models from ecology, economics and cognition, yet when we put these parts together we get behaviour that is completely novel and unpredictable,” says Stephen Carpenter, one of the researchers and a professor at the University’s of Wisconsin-Madison’s Center for Limnology.

The researchers believe their results demonstrate the need for a more flexible attitude toward resource management. Although players could not avoid occasional periods of eutrophication, they were able to alter their behaviour to limit the frequency and severity of these periods. Players who were willing to experiment with the different levels of phosphorus inputs and change their strategy regularly were more successful.

The key, the researchers claim, is to experiment, learn and adapt. “Frozen policy is a route to disaster,” the researchers write. “If policies are fixed, or experimental explorations of the stability domain are too timid, the manager cannot learn quickly enough to make the adjustments that are needed to sustain the social and ecological system.” Inevitably, systems crash or undergo dramatic change, and the only way for managers to soften the effect is by rolling with the punches and changing their tack regularly.

In the past, ecological models have rarely taken human decision-making into account, and economic analyses often ignore the complexity of natural systems. As a result, theory-based approaches to resource management have a poor success record. The researchers hope that cross-disciplinary models will eventually bridge the gap between theory and practice.

The researchers are proponents of a school of ecological thought, which argues that ecosystems are dynamic and non-linear, and go through periods of organisation and collapse. They believe that if resource managers acknowledge the non-linear, resilient nature of the systems they manage, they stand a better chance of achieving sustainable production. This attitude differs markedly from the traditional attitude of policy-makers and land managers, who usually set specific goals, expect linear results from their actions, and are often disappointed when a resource system fails to respond directly to their actions.

The researchers point out that their model is a first step. “We encourage the exploration of a wide range of alternative models that integrate non-linear ecological dynamics, at slow and fast time scales, with complex social systems,” they write. “We will be surprised if the models we have introduced here are not obsolete within a short time.”