Biodiversity Loss Threatens Human Well-Being Sandra Díaz*, Joseph Fargione, F

Essay Biodiversity Loss Threatens Human Well-Being Sandra Díaz*, Joseph Fargione, F. Stuart Chapin III, David Tilman he diversity of life on Earth is processes and, thus, human well-being; studies. The fi rst is that the number dramatically affected by human and (c) such consequences will be felt and strength of mechanistic Talterations of ecosystems [1]. disproportionately by the poor, who are connections between biodiversity Compelling evidence now shows that most vulnerable to the loss of ecosystem and ecosystem processes and services the reverse is also true: biodiversity in services. clearly justify the protection of the broad sense affects the properties the biotic integrity of existing and of ecosystems and, therefore, the What We Do Know: Functional restored ecosystems and its inclusion benefi ts that humans obtain from Traits Matter Most in the design of managed ecosystems. them. In this article, we provide a Biodiversity in the broad sense is the All components of biodiversity, synthesis of the most crucial messages number, abundance, composition, from genetic diversity to the spatial emerging from the latest scientifi c spatial distribution, and interactions arrangement of landscape units, may literature and international assessments of genotypes, populations, species, play a role in the long-term provision of the role of biodiversity in ecosystem functional types and traits, and of at least some ecosystem services. services and human well-being. landscape units in a given system However, some of these components Human societies have been built (Figure 2). Biodiversity infl uences are more important than others in on biodiversity. Many activities ecosystem services, that is, the benefi ts infl uencing specifi c ecosystem services. indispensable for human subsistence provided by ecosystems to humans, The evidence available indicates that lead to biodiversity loss, and this trend that contribute to making human life it is functional composition—that is, is likely to continue in the future. We both possible and worth living [4] (Box the identity, abundance, and range of clearly benefi t from the diversity of 1). As well as the direct provision of species traits—that appears to cause organisms that we have learned to use numerous organisms that are important the effects of biodiversity on many for medicines, food, fi bers, and other for human material and cultural life ecosystem services. At least among renewable resources. In addition, (Figure 1, path 1), biodiversity has species within the same trophic level biodiversity has always been an integral well-established or putative effects on a (e.g., plants), rarer species are likely part of the human experience, and number of ecosystem services mediated to have small effects at any given point there are many moral reasons to by ecosystem processes (Figure 1, path in time. Thus, in natural systems, if preserve it for its own sake. What has 2). Examples of these services are we are to preserve the services that been less recognized is that biodiversity pollination and seed dispersal of useful ecosystems provide to humans, we also infl uences human well-being, plants, regulation of climatic conditions should focus on preserving or restoring including the access to water and basic suitable to humans and the animals materials for a satisfactory life, and and plants they consider important, Citation: Díaz S, Fargione J, Stuart Chapin F III, security in the face of environmental the control of agricultural pests and Tilman D (2006) Biodiversity loss threatens human change, through its effects on the diseases, and the regulation of human well-being. PLoS Biol 4(8): e277. DOI: 10.1371/journal. pbio.0040277 ecosystem processes that lie at the core health. Also, by affecting ecosystem of the Earth’s most vital life support processes such as biomass production DOI: 10.1371/journal.pbio.0040277 systems (Figure 1). by plants, nutrient and water cycling, Copyright: © 2006 Díaz et al. This is an open-access Three recent publications from the and soil formation and retention, article distributed under the terms of the Creative Millennium Ecosystem Assessment biodiversity indirectly supports the Commons Attribution License, which permits unrestricted use, distribution, and reproduction in [2–4], an initiative involving more production of food, fi ber, potable any medium, provided the original author and source than 1,500 scientists from all over the water, shelter, and medicines. The links are credited. world [5], provide an updated picture between biodiversity and ecosystem Sandra Díaz is principal researcher and associate of the fundamental messages and key services have been gaining increasing professor of ecology and biogeography at Instituto challenges regarding biodiversity at the attention in the scientifi c literature of Multidisciplinario de Biología Vegetal (CONICET- global scale. Chief among them are: UNC) and FCEFyN, Universidad Nacional de Córdoba, the past few years [2–4,6]. However, Argentina. Joseph Fargione is research assistant (a) human-induced changes in land not until now has there been an effort faculty at the Department of Biology, University of cover at the global scale lead to clear to summarize those components New Mexico, Albuquerque, New Mexico, United States of America. F. Stuart Chapin III is professor of losers and winners among species in of biodiversity that do, or should, ecology at the Institute of Arctic Biology, University of biotic communities; (b) these changes matter the most for the provision of Alaska at Fairbanks, Fairbanks, Alaska, United States have large impacts on ecosystem these services, and the underlying of America. David Tilman is the McKnight Presidential Chair in Ecology at the Department of Ecology, mechanisms explaining those links Evolution and Behavior, University of Minnesota, St. (Table 1; see also [3]). Paul, Minnesota, United States of America. Essays articulate a specifi c perspective on a topic of A few key messages can be drawn broad interest to scientists. * To whom correspondence should be addressed. from existing theory and empirical E-mail: [email protected] PLoS Biology | www.plosbiology.org 1300 August 2006 | Volume 4 | Issue 8 | e277 Box 1. From Ecosystem Processes to Human Well-Being Ecosystem processes are intrinsic processes and fl uxes whereby an ecosystem maintains its integrity (such as primary productivity, trophic transfer from plants to animals, decomposition and nutrient cycling, evapotranspiration, etc.). They exist independently from human valuation, and their magnitude and rate can be established regardless of the cultural, economic, and social values and interests of different human groups (Figure 1, Ecosystem Processes box). Ecosystem services are the benefi ts provided by ecosystems that contribute to making human life both possible and worth living. Ecosystem services are context- dependent; that is, the same ecosystem process can produce an ecosystem service that is highly valued by one society or stakeholder group but not highly valued by other societies or groups. Some ecosystem services involve the direct provision of material and non-material goods and are associated directly with the presence of particular species of plants and animals—for example, food, timber, medicines, and ritual materials (Figure 1, path 1 and bottom sub-box of Ecosystem Services box). Other ecosystem services arise, either directly or indirectly, from the continued functioning of ecosystem processes. For example, the service of formation, retention, and sustained fertility of soils necessary for the production of plants and animals considered important by different human societies depends on the ecosystem processes of decomposition, nutrient cycling by soil microbiota, and the retention of water and soil particles by a well-developed root network (Figure 1, path 2 and top sub-box in red of Ecosystem DOI: 10.1371/journal.pbio.0040277.g001 Services box). Some authors (e.g., [30]) have advocated a stricter defi nition of ecosystem Figure 1. Biodiversity Is Both a Response services as components of nature that are directly enjoyed, consumed, or used in order Variable Affected by Global Change Drivers to maintain or enhance human well-being. Although such an approach can be useful and a Factor That Affects Human Well-Being when it comes to ecosystem service accounting, our emphasis here is conceptual, and Links developed in this article are indicated in red. In the biodiversity box, the hierarchical therefore we prefer to use the broader, widely accepted defi nitions and classifi cation components of biodiversity (genotypes, adopted by the Millennium Ecosystem Assessment [4]. This is because some ecosystem species, functional groups, and landscape services (e.g., food provision) can be quantifi ed in units that are easily comprehensible units) each have the characteristics listed by policy makers and the general public. Others—for example, the services that in the sub-box and explained in Figure 2 (number, relative abundance, composition, regulate and support the production of tradable goods—are more diffi cult to quantify. spatial distribution, and interactions involved If a criterion based on economic accounting is applied too strictly, there is a risk in “vertical” diversity). that ecosystem service assessment could be biased toward services that are easily Modifi ed from [3,4]. quantifi able, but not necessarily the most critical ones [29]. Human well-being is a human experience that includes the basic materials for a good life, freedom of choice and action, health, good social relationships, a sense of cultural identity, and a sense of security. The sense of well-being is strongly dependent on the specifi c cultural, geographical, and historical context in which different human societies develop, and is determined by cultural-socio- economic processes as well as by the provision of ecosystem services. However, the well-being of the vast majority of human societies is based more or less directly on the sustained delivery of fundamental ecosystem services, such as the production of food, fuel, and shelter, the regulation of the quality and quantity of water supply, the control of natural hazards, etc. (see Figure 1, path 3).

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