SUBJECT: Consequences of biodiversity loss for ecosystem processes and services
AUTHOR: Michel Loreau
DATE: 3rd April 2003

KEYWORDS: Biodiversity, ecosystem functioning, species functional complementarity.

SUMMARY: Biodiversity loss will have significant impacts on ecosystem functioning and ecosystem services; these impacts need to be known to assess their long-term socio-economic consequences.


The relationship between biodiversity and ecosystem functioning has emerged as a central issue in ecological and environmental sciences during the last decade (see recent syntheses in Kinzig et al. 2002; Loreau et al. 2002). Increasing domination of ecosystems by humans is steadily transforming them into depauperate systems. Because ecosystems collectively determine the biogeochemical processes that regulate the Earth system, the potential ecological consequences of biodiversity loss have aroused considerable interest.

Recent experimental and theoretical work in this area has shown that the productivity and nutrient retention ability of grassland ecosystems are adversely affected by loss of species and functional diversity. The main mechanisms responsible for these effects are functional complementarity among species with different ecological niches and regional stochastic processes involved in community assembly. Although the significance and implications of these mechanisms have been debated, it has now been clearly established that functional complementarity among species drives most of the biodiversity effects observed in recent experiments. Other studies have provided similar conclusions for other systems, but the nature and extent of biodiversity effects on ecosystem processes are dependent on the ecosystem and the process considered.

These short-term, small-scale experiments are likely to underestimate the true extent of the functional impacts of biodiversity loss. First, there is theoretical and experimental evidence that the diversity of functionally similar species can also buffer ecosystem processes, and hence provide biological “insurance”, against environmental fluctuations. Second, heterogeneous environments are best used by an array of species with different specialisations, and habitat destruction and fragmentation may prevent appropriate dominant species from being recruited in each community. The larger the temporal and spatial scales considered, the higher the diversity that is likely to be needed to maintain particular ecosystem processes.

Recent scientific advances support neither the catastrophist view that the biosphere will collapse as a result of biodiversity loss, nor the optimistic view that nature can be further despoiled without any consequences for human societies. Changes in biodiversity will have significant impacts on the functioning of natural and managed ecosystems, and thereby on the services they provide to human societies. These impacts need to be known to assess their long-term socio-economic consequences. How much biodiversity loss we are willing to accept, however, is a societal choice.

References
Kinzig, A. P., Pacala, S. W. and Tilman, D. (eds) 2002. The functional consequences of biodiversity: empirical progress and theoretical extensions. Princeton University Press, Princeton.
Loreau, M., Naeem, S. and Inchausti, P. (eds) 2002. Biodiversity and ecosystem functioning: synthesis and perspectives. Oxford University Press, Oxford.

A contribution by:

Michel Loreau
Laboratoire d’Ecologie, Ecole Normale Supérieure, UMR 7625,
46 rue d’Ulm, F–75230 Paris Cedex 05, France