Diversity-function debate
Encyclopedia
Definitions
Species diversity: the total number of species in an area; also, the proportional distribution of species in a given area.Functional diversity: the number of functional roles represented in an ecosystem.
Issues in Ecology
Functional diversityEcological effects of biodiversity
The diversity of species and genes in ecological communities affects the functioning of these communities. These ecological effects of biodiversity in turn affect both climate change through enhanced greenhouse gases, aerosols and loss of land cover, and biological diversity, causing a rapid loss...
, composition, and species diversity
Species richness
Species richness is the number of different species in a given area. It is represented in equation form as S.Species richness is the fundamental unit in which to assess the homogeneity of an environment. Typically, species richness is used in conservation studies to determine the sensitivity of...
affect the biogeochemical processes of ecosystems. However, the degree to which these factors influence ecosystems and whether that influence is significant is much debated. In the article "The Influence of Functional Diversity and Composition on Ecosystem Processes," scientists reported on an experiment in which they studied the effects of plant species diversity, functional diversity, and functional composition on ecosystem processes, as measured in six response variables (productivity, plant % N, plant tot. N, soil NH4, soil NO3, and light penetration). 289 plots were designed with varying amounts of the three controlled factors. Each plot contained up to 32 perennial savannah-grassland species representing up to five plant functional groups. These species were not equal in their functional impact to the ecosystem.
The statistical results show that functional diversity and composition significantly affected the six response variables to a greater extent than species diversity. By themselves, all three factors significantly affected ecosystem processes and also influenced each other. The mechanisms and degree by which they influenced each other are unclear. The Tilman article doesn’t purport to have the definite answer. Uncertainty is implied in the major conclusions of the paper: “ . . . the number of functionally different roles represented in an ecosystem may be a stronger determinant of ecosystem processes than the total number of species, per se. However, species diversity and functional diversity are correlated. . .” This study implies that to progress, scientists on both sides of the diversity-function debate must develop a holistic model that acknowledges the inextricable relationship between diversity and function.
In the fourth installment of the Bulletin of the Ecological Society of America
Ecological Society of America
The Ecological Society of America is a professional organization of ecological scientists. Based in the United States, ESA publishes a suite of publications, from peer-reviewed journals to newsletters, fact sheets and teaching resources. It holds an annual meeting at different locations in the...
’s “Issues in Ecology” series, the Tilman et al. study was used to support the argument for a positive correlation between diversity and productivity. Following its release, the “Issues” authors were accused of being deliberately misleading, presenting controversial findings as fact. Wardle charged that the diversity experiments reported in Tilman et al., despite being stated in “Issues” as solid fact, were confounded by an experimental design that assumed “that biological communities are randomly assembled with regard to the ecosystem property being investigated.” This phenomenon is termed the “selection probability effect.” The “Issues” article, however, does not present this opinion as fact. It discusses the “sampling effect”
Ecological effects of biodiversity
The diversity of species and genes in ecological communities affects the functioning of these communities. These ecological effects of biodiversity in turn affect both climate change through enhanced greenhouse gases, aerosols and loss of land cover, and biological diversity, causing a rapid loss...
as a possible mechanism, not as an irrefutable mechanism. Furthermore, its conclusions are marked by uncertainty: although species diversity and functional diversity are correlated, functional diversity may play a larger role in ecosystem processes than the total number of species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
.
Some of the services provided by ecosystems include the components used in fabricating food, clothing, medicine, and energy production. Recreation and passive ecosystem services are significant as well. These include fishing, hunting, hiking, birding, camping, water filtration/purification, climate moderation, flood mitigation, erosion prevention, and pest management
Integrated Pest Management
Integrated pest management is an ecological approach to agricultural pest control that integrates pesticides/herbicides into a management system incorporating a range of practices for economic control of a pest...
.
As reported in "Expert Estimates About Effects of Biodiversity on Ecosystem Processes and Services," ecosystem process rates correlate strongly with biodiversity, and these processes are crucial for ecosystem services.