Biodiversity and Ecosystem function

Introduction

In recent years, the recognition that species may play important roles in ecosystems and the rapidly emerging interest in the biodiversity conservation have prompted ecologists to ask new questions on the relationships between `diversity' and `ecosystem function' (for example, Walker, 1992; Schultze and Mooney, 1993; Jones and Lawton, 1995; Johnson et al., 1996).

Why it is important?

One reason for the interest in the functional role of biodiversity (rather than structural) in ecosystems is that society might be more likely to take action to preserve biodiversity if it could be shown that there was some direct economic gain by doing it (Bengtsson, 1998). Over the last fifteen years, an increasing number of studies have focused on biodiversity. This is principally because the world’s flora and fauna are disappearing at rates greater than during historical mass extinction events (Chapin et al, 2001). As recently suggested by Thomas et al. (2004), there is an 18 to 35% risk of species-level extinction resulting from climate changes by the year 2050. Moreover, other processes, for example, agricultural expansion in response to an increasing demand for food, have a negative impact on biodiversity as a result of habitat destruction (Tilman et al., 2001; Humbert and Dorigo, 2005).

Biodiversity and Ecosystem function are central to both community and ecosystems ecology and need to be understood to predict, for example, how communities and ecosystems respond to environmental change (Bengtsson, 1998) and on understanding how declining diversity influences ecosystem services on which humans depend (Duffy, 2003).

Research on Ecosystem Functioning

Research on Biodiversity - Ecosystem Functioning (the BEF agenda) has stimulated a new and highly productive intercourse between population, community, ecosystem, and conservation ecology (Kinzig et al. 2002; Loreau et al. 2002; Duffy, 2003). Most experimental evidence for biodiversity effects on ecosystem functioning has come from terrestrial ecosystems, particularly grasslands (Naeem et al. 1994, Tilmann et al. 1997a, Hector et al. 1999, Schmid et al. 2001; Giller et al., 2004). These studies have shown that changing biodiversity in natural ecosystems is likely to have much more complicated impacts on ecosystem functioning than predicted from changes in plant diversity alone (Duffy, 2003). For example in trophic levels of plant communities, as diversity is lost from a system, impacts will also depend from the loss of predators which will evoke change in the structure of all trophic levels (Hairston et al. 1960; Power 1990; Estes et al. 1998; Duffy, 2003).

The mosaic of habitat patches in aquatic systems often is more spatially compact than in terrestrial environments, presenting more tractable experimental systems at the landscape scale (Schindler and Scheuerell 2002). Because each aquatic ecosystem is composed of multiple habitat types, assessing the effects of biodiversity changes on the functioning of aquatic ecosystems requires experimental designs that allow a scaling up from individual homogenous patches to large scale, often highly heterogeneous areas (Giller et al. 2004).