NEWS STORY: Understanding how ecosystems function
Lessons from a remote Antarctic island on the vulnerability of ecosystems
Scientists have carried out new research that could change the way we think about the vulnerability of ecosystems. Published in Ecology Letters this week, their findings show that the long standing debate about what makes an ecosystem resilient may be missing the point entirely, providing an important insight into how they work.
Many natural ecosystems are impacted by human-induced changes, such as fishing, deforestation and climate change. Damage to one species within an ecosystem can seriously affect the entire community, as the balance between predators and prey is altered. Reliable mathematical models provide a way to investigate how ecosystems will respond to such external environmental changes as well as to various management approaches.
Researchers from the British Antarctic Survey (BAS) used data gathered on Signy, one of the South Orkney Islands, to explore how the relationships between the interacting species in the tundra ecosystems on this island are preserved…that is, how stable they are when confronted by small disturbances. Detailed observations of the energy transfer between the species in the food web allowed the researchers to develop a model informed by reliable real-world measurements.
Michael Thorne from the British Antarctic Survey explains:
“The terrestrial ecological systems in the Antarctic provide a fantastic natural laboratory from which the fundamental behaviour of vastly more complex ecosystems can be understood.
“The British Antarctic Survey maintained two sites on Signy Island in the 1970s and focussed a great deal of effort in understanding all the constituent species, their life cycles and their interactions. The material flow through the whole system was measured, from the mosses and detritus, or dead organic matter, through the bacteria, to the largest terrestrial organism, the mite.
“Because of the systems’ relative biological simplicity, we were able to dig deeply, with a confidence that is unique in large-scale ecological studies, into the forces playing the strongest role in shaping the checks and balances that maintain ecosystem stability.”
For many years ecological theory has centred on the diversity of species and interactions within a community. The BAS researchers found their measurements showed a totally different perspective. Rather than focussing on the number of species in a particular community, their findings suggest we should look at the way in which these species interact with each other and how much energy is transported between them.
Anje-Margriet Neutel from the British Antarctic Survey explains:
“Ecologists have long debated the question of whether the diversity or complexity of ecosystems enhances their stability or jeopardises it. We show that this discussion is irrelevant. It is not about how many species or interactions there are, but how strongly they interact, and where these relationships fit into the food web.
“Of course, the diversity of species is important. In diverse communities species can take over each other’s roles, acting as a buffer to outside disturbance. But communities can be stable whether they have many or few species.
“To understand the future stability of ecological systems in the face of external changes, such as climate change, we must work to understand the strength of the interactions between particular species.”
The study opens up many new avenues for research of the stability of ecological communities and will eventually allow scientists to identify which ecosystems are most threatened by external changes, and how to manage them in a sustainable way.
Notes for editors
Food webs are networks of consumption relationships. Each of the interactions in a particular food web is shaped by the processes such as predation and competition for resources. It has generally been believed that, at the larger scale, the behaviour of such networks depends on the number of interacting species and connections. The BAS researchers were able to show that this idea is incorrect. They showed that the energy flow between species in those eating and being eaten relationships dominates the behaviour of the whole, complex, ecosystems, and not the diversity or connectivity.
The paper, “Interaction strengths in balanced carbon cycles and the absence of a relation between ecosystem complexity and stability” is published by Ecology Letters. Authors: Anje-Margriet Neutel and Michael A.S. Thorne.
Issued by the British Antarctic Survey Press Office.
Paul Seagrove, Tel: +44 (0)1223 221414; +44 (0)7736 921693) email: [email protected]