|3.||Ecosystem services, trade-offs, and biodiversity|
|5.||Substituting for ecosystem services|
|6.||Ecosystem services and conservation|
Ecosystem services are defined as “the multiple benefits provided by ecosystems to humans” (The Millennium Ecosystem Assessment, 2005). In other words, ecosystem services are only services to the extent that they support human well-being and are thus an inherently anthropocentric construct. Analysts cannot understand how the delivery of ecosystem services has changed over time solely from a purely natural science analysis of ecological patterns, processes, or functions. They must also understand what people value and how much they value it. Ecological dynamics could remain constant, but the services people derive from ecosystems could still change as people’s values or circumstances change. Ecosystems could degrade, from a purely ecological perspective, but that degradation of ecological systems could still support an enhanced flow of services from humanity’s perspective. Any adequate assessment of the flow of ecosystem services, or any assessment of how best to manage ecological systems to maximize the benefits people receive from them, must join ecological and social analyses.
However, this is a guide to ecology, and therefore, this section primarily contains contributions by ecologists. Ecologists obviously have much to contribute to an understanding of ecosystem services. In this section, various authors cover issues of scale (Scholes, chapter VI.1), biodiversity-ecosystem functioning relationships (Naeem, chapter VI.2), and critical aspects of ecological organization (Norberg, chapter VI.3), among other things. Authors examine ecosystem services in agroecosystems (Power et al., chapter VI.4), forests (Solórzano and Páez-Acosta, chapter VI.5), grasslands (Downs and Sala, chapter VI.6), and marine ecosystems (Baskett and Halpern, chapter VI.7). Other authors analyze different types of services, from tangible and consumable goods such as fresh water (Palmer and Richardson, chapter VI.8) to the more intangible and esoteric cultural or spiritual services provided by the world’s ecological systems, and other services in between (Daszak and Kilpatrick on regulating services in chapter VI.9; Pergams and Kareiva on genetic diversity in chapter VI.10). But ultimately, the ecological analyses are just the starting point—knowing how ecological functions are changing, although relevant to adequate comprehension and appropriate management of ecosystem services, is not enough. The social value placed on those services— the human desires that translate a mere ecosystem function into a beneficial service—are half the equation. I have thus chosen to close this section with two nonecological chapters (which obviously can not do full justice to the second half of the equation): one focuses on the economics of ecosystem services (Perrings, chapter VI.11) and the other on how technological innovation has altered the need for, and therefore value placed on, various services (Goklany, chapter VI.12). This section closes with an exploration of how a focus on ecosystem services, rather than species richness per se, might alter conservation practices and outcomes (Rodríguez, chapter VI.13). I return to many of these issues—on the interplay between the social and ecological components of ecosystem services—in the topics I highlight below.
The recognition that ecological systems benefit humans must, in some sense, be as old as humanity itself—every culture or social group that I know of has developed rituals aimed at influencing Nature and her bounty. Even the more scientific assessment of ecological services has a deep history; Plato, for instance, recognized