They find that the specialisation of different plant species to different roles fundamentally affects the way that ecosystems work, suggesting a new reason to conserve a variety of species.
A new analysis of the results of a wide-ranging ecological experiment across Europe, named the BIODEPTH project (2), shows that communities of plants grow better when they consist of teams of species that are complementary to one another.
Early results from the project showed that harvest yields were higher when a range of plant species were grown together, but could not explain why this occurred.
The new analysis reveals that complementary interactions between species appear to play a stronger role than 'selection effects' (where dominance by species with particular traits affects ecosystem processes).
In the real world this could mean that the amount of energy turned into plant life - the 'productivity' of an ecosystem - also declines when species are missing.
This new appraisal of the BIODEPTH data represents the latest development in a scientific debate about how the loss of biodiversity affects the way in which ecosystems work.
It may help recent efforts among ecologists to reach a consensus in that debate, as it demonstrates that both numbers of different plants and their types (3) play important roles in ecosystems through their individual characteristics and the ways they interact with one another.
Dr Andy Hector of the NERC Centre for Population Biology at Imperial College, London, and co-author of the report, said:
"Our research shows biodiversity is not just a pretty face - it can also affect the way the environment works.
Previous justifications for conserving biodiversity have taken in aesthetic and ethical reasoning: that we like some of it and that it is 'wrong' to let it go extinct. Here we suggest, along with the findings of other ecologists, that there is another, complementary reason to preserve diversity - it plays a role in determining the way the environment works.
These results provide the type of general ecological principles that need to be considered when setting conservation and habitat management policy."
First author, Professor Michel Loreau of the Ecole Normale Superieure, Paris, said:
"This paper makes a significant contribution to resolving the debate about ecosystem functioning by providing a novel method and new data that show how complementary interactions between species appear to play the stronger role."
The EU-funded BIODEPTH project, which ran from 1996 to 1999, performed an identical experiment in eight different countries which assembled miniature experimental grasslands at field sites around Europe from Greece to Sweden (4).
The "mini-meadows" varied in plant diversity to mimic the gradual loss of species seen throughout Europe.
Authors Drs Loreau and Hector took a new approach to the analysis of the BIODEPTH data, whose key findings were published in Science in November 1999, by adapting a classic method normally used to analyse evolutionary changes.
A commentary accompanying publication of the earlier BIODEPTH results in Science praised the project for its high degree of multinational collaboration within European science.
For more information please contact:
Dr Andy Hector
NERC Centre for Population Biology
Imperial College at Silwood Park
Professor Michel Loreau
Lab d'Ecologie, UMR 7625
Ecole Normale Superieure, Paris
Dr Glen Dawkins, Manager
NERC Centre for Population Biology
Imperial College at Silwood Park
BIODEPTH web site: www.cpb.bio.ic.ac.uk/biodepth/contents.html
BIODEPTH Results and Relevance web site: www.cpb.bio.ic.ac.uk/biodepth/results_and_relevance.html
Results and Relevance is a web resource aimed at non-specialists looking for information explaining biodiversity and ecosystem functioning and the undertaking of BIODEPTH - now that the project is completed and the results and policy implications are becoming evident.
Notes to Editors
1. The research is reported in the article "Partitioning selection and complementarity in biodiversity experiments" by M. Loreau and A. Hector published in the peer-reviewed journal, Nature Vol. 411 Issue 6842 on Thursday 5 July 2001. Embargoed copies of the final edited version of the article should be requested from Jo Webber, Press Administrator at Nature. Telephone: 44-20-7843-4571 Email: email@example.com Web site: press.nature.com/
2. BIODEPTH (Biodiversity and Ecological Processes in Terrestrial Herbaceous Ecosystems) was funded by the EC Framework IV Environment and Climate Programme (contract ENV-CT95-0008).
3. 'Types' of plants refers to the 'functional group' classification used by ecologists. In this research, three different functional groups were represented: grasses, nitrogen-fixing legumes, and non nitrogen-fixing herbs.
4. BIODEPTH field sites are in Bayreuth, Germany; Lisbon, Portugal; Lupsingen, Switzerland, Lesbos, Greece; Cork, Ireland; Umea, Sweden; and Sheffield and Ascot in the UK. The project consortium includes a mathematical modeling group lead by Michel Loreau in Paris, France.
5. The Centre for Population Biology, established in 1989, is funded by the UK Natural Environment Research Council (NERC), and is hosted by Imperial College where it is part of the Department of Biological Sciences on its Silwood Park campus. It publishes about 90 papers per year and its core mission is to conduct basic research in population biology and related disciplines to understand and predict the functioning of ecosystems. The CPB receives UKP1.1 million core funding per year. Web site at: www.cpb.bio.ic.ac.uk/
6. The UK's Natural Environment Research Council funds and carries out impartial scientific research in the sciences of the environment. NERC trains the next generation of independent environmental scientists. For more information visit their website at www.nerc.ac.uk
7. The Ecole Normale Superieure is an institution of higher education created during the French Revolution. The ENS educates students in both humanities and sciences and prepares students for the award of university diplomas. The ENS houses a number of significant laboratories which accommodate up to 1000 researchers, and which are considered the best in their fields in France. These laboratories are intended for fundamental research, but are biased towards the applied sciences. Web site : www.ens.fr
8. Imperial College of Science, Technology and Medicine is the largest applied science, technology and medicine university institution in the UK. It is consistently rated in the top three UK university institutions for research quality, with one of the largest annual turnovers (UKP339 million in 1999-2000) and research incomes (UKP176 million in 1999-2000). Web site: www.ic.ac.uk