Whether an animal or plant community remains stable despite external impacts does not depend on biological diversity alone: asynchrony across the species is also a crucial factor. The more the species in an ecosystem fluctuate in their evolution over time, the less they are likely to falter. As a result, diversity takes second place in terms of the factors to be considered in the context of ecosystem stability. A team of scientists spearheaded by the Technical University (TU) Munich and TU Darmstadt have published these findings on 12 February in the journal “Nature Communications”.
The long-term functioning of ecosystems depends on the stability of their species communities, as these ensure the functioning of the entire system life cycle. However, land use by humans causes a reduction of the number of species in many ecosystems. Accordingly, when it comes to conserving species diversity and providing sustainable protection for natural resources, the stability of such animal and plant communities is the main goal of nature conservation and ecosystem management. In principle, higher species diversity and greater asynchrony can increase the stability of the species community. But if land use is intensified or changed, which of these factors — species diversity or asynchrony — is more important?
The effect of land use
For their study, the researchers evaluated over 2,600 species ranging from insects and spiders, to birds and bats and through to herbaceous grasses over a period of six years. Data from 150 forests and 150 pastures and meadows located in three regions in Germany were collated. “The results show that a change in the use of a landscape, for example when a managed forest is converted into grassland, destabilizes the animal and plant community,” explains Dr. Martin Goßner from the Terrestrial Ecolology Research Group at the TU Munich.
“Similarly, the intensification of land use results in the destabilization of the animal and plant community and this, in turn, impairs the entire ecosystem,” adds Dr. Nadja Simons (also from the TU Munich). Animal communities presented a stronger reaction here than their plant counterparts. The most severe reaction by far was observed among birds and bats, which can therefore be seen as indicators of land-use intensity.
The more diverse the species, the more stable the ecosystem
Scientists have long hypothesized that biodiversity is of critical importance to the stability of natural ecosystems and their abilities to provide . This assumption has just recently been proven in a study of which the findings have been published online on 13 January in the journal Nature.
In addition to the diversity of species being important for the stability of ecosystems the new insights gained in the recent study are that the asynchrony of the species is important as well. In fact, the extent to which the asynchrony of the species can increase the stable interplay of animals and plants in an ecosystem is new. Nico Blüthgen says, “We can compare it to the stock exchange, where risk-averse investors are encouraged not to put all their eggs in one basket and to create a portfolio of different securities instead. This is referred to as the portfolio effect. And, just as in nature, in order to cushion the impact of fluctuations in the investments over time, it is important that the portfolio not only contains a lot of investments but also differ types of investments.” Asynchrony thus assumes a key role in the interaction between diversity and stability. The scientists plan to investigate the factors that lead to greater asynchrony in further studies.
This joint project by several research groups was the most comprehensive study on the topic of stability to date and was carried out in the context of the “Biodiversity Exploratories” research alliance. This alliance is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation). One of its express aims is to facilitate long-term studies of this kind, as impacts on the stability of ecosystems can only be studied effectively from a long-term perspective.
(Source: Technische Universität München press release, 12.02.2016)