Population diversity and ecosystem services

https://doi.org/10.1016/S0169-5347(03)00100-9Get rights and content

Abstract

The current rate of biodiversity loss threatens to disrupt greatly the functioning of ecosystems, with potentially significant consequences for humanity. The magnitude of the loss is generally measured with the use of species extinction rates, an approach that understates the severity of the problem and masks some of its most important consequences. Here, we propose a major expansion of this focus to include population diversity: considering changes in the size, number, distribution and genetic composition of populations and the implications of those changes for the functioning of ecosystems and the provision of ecosystem services. We also outline the key components of population diversity and describe a new approach to delineating a population unit that explicitly links it to the services that it provides

Section snippets

Defining population units and the importance of population change

There are many approaches to defining species populations 17, 18, 19, 20, 21, 22. Consistently problematic is defining population boundaries so that the number of populations can be clearly determined [6]. Geneticists use measures of gene flow and genetic differentiation to distinguish one population from another [23]. In a demographic sense, this can be achieved by careful measures of individual movement (e.g. [24]), which enables the delineation of populations that are sufficiently isolated

Key components of population diversity

There are four key components of population diversity: richness, the size of each population, spatial distribution and differentiation.

Population change and biodiversity decline

We raise two crucial issues in this article. First, focusing on changes in population diversity is a more compre-hensive assessment of biodiversity decline than is a narrow emphasis on the loss of species alone. Rough estimates of large-scale population loss have already been attempted 5, 6. We argue that consideration of population size, distribution, genetic differentiation and density are also needed to reflect accurately the consequences of population change. This focus requires a

Acknowledgements

Carol Boggs, Jennifer Hughes, Claire Kremen, John Lawton, Michael Soulé, Taylor Ricketts, Brian Walker and four anonymous referees provided valuable comments about this article. We thank the Moore Family Foundation, the Winslow Foundation, and Peter and Helen Bing for support.

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