From an October 2005 Position Statement of the Ecological Society of America (ESA), a nonpartisan, nonprofit organization of scientists founded in 1915.*
 
Human beings are currently altering the composition of species in ecosystems worldwide, to an extent equivalent to the largest extinctions in prehistoric times. These human changes to biodiversity raise concern for ethical and aesthetic reasons, but they also have a strong potential to adversely affect ecosystems and the goods and services they provide us, since human beings derive many benefits from ecosystems.
 
The current changes occurring in the biodiversity of ecosystems can involve multiple levels of biological organization, including altering the genetic variety within species, the individual species that exist within communities, and the ecosystem types within landscapes. They include loss of native diversity as well as invasion by exotic species.
 
However, many strategies exist to help minimize these negative ecological effects while at the same time maintaining or improving economic well-being and human quality of life. Efforts to minimize human impacts on biodiversity also provide the opportunity to safeguard the benefits humans derive from ecosystems. By including biodiversity in public policy and land management in ways that minimize adverse changes to biodiversity, society will take an important step toward responsibly managing Earth’s ecosystems.
 

Consequences of Biodiversity Loss

The consequences of biodiversity loss are more dramatic when considered over longer time periods, larger areas, and a broader array of ecosystem services. For example:
 
– Species diversity in ecosystems can stabilize the response of an ecosystem over time to fluctuations in environmental conditions. In diverse ecosystems in which multiple species may carry out similar roles, some ecosystem services can be initially insensitive to partial loss of species For example, both the diversity of harvested species and the genetic diversity within those species help reduce the susceptibility of agriculture and forest production to diseases and altered climate. Loss of this buffering capacity (which is provided by rich biodiversity) could weaken the resilience of ecosystems to natural climate variability, extreme events and environmental change. There are counterexamples in which higher diversity of some types of species can lead to greater susceptibility to certain disturbances, as when an important host organism is present that lets a pest species complete a complex life cycle. The appropriate mix of species for a given management goal is as important as simple numbers of species.
 
– Species diversity is important for management over large spatial scales and forms the basis for regional conservation planning. As environmental conditions change, different species, and different genetic varieties within the same species, are more or less adapted to local conditions over large areas. For example, foresters often draw on information about genetic and species diversity to match regional seed sources and species with appropriate growing conditions. Also, high regional species diversity is necessary to maintain even modest local diversity in parks and reserves. This may be of increasing importance in the face of climate change. Finally, many far-ranging species such as migratory birds and fishes require connections among a variety of ecosystems along their traveling routes. Protection and restoration of habitat diversity and linkage will help maintain such species and the goods and services associated with them.
 
– Recognizing the importance of diversity is vital to management for multiple ecosystem services. Focusing on only a single management goal can lead to the loss of species important for other ecosystem services. Adaptive management can help achieve multiple concurrent goals and maintain options for achieving new ones in the future. For example, National Forests are managed simultaneously for timber harvest, wildlife protection, and recreation. Although the trees are important to all of these ecosystem services, many other species make the attainment of other management goals possible.
 

Guidelines for Policy

We must manage biodiversity intelligently while maintaining or improving economic well-being and human quality of life. Here are some guidelines for policies that can help us do both.
 
1. Policy and management should account for adverse effects on biodiversity which, in pursuit of some management goals, results in the loss of other services. Many changes to biodiversity are a by-product of activities meant to improve human well-being, such as food production, manufacturing, housing development, and transportation. Often, however, an unintended consequence is loss of biodiversity which undermines other benefits to society. Similarly, management choices targeting important agricultural, forestry, or fisheries species can influence many species beyond those that are directly harvested for human food or use. Non-harvested species often play important supporting roles, such as pest control (e.g., predatory insects surrounding farmland), pollination (many species of insects, birds, and bats), provision of habitat (e.g., eelgrass beds for fisheries), and serving as food sources for harvested (e.g., wild fisheries) or charismatic species that drive ecotourism. Proper identification and valuation of these services is essential to a complete accounting of management costs and benefits.
 
2. Recognition is needed that adverse changes in ecosystem services can occur long before a species goes extinct. For example, large reductions in formerly abundant species, or loss of a species from part of its range, raise concern because these changes in abundance or localized extinctions have the greatest direct effect on ecosystem processes. If declining abundances are left unchecked, extinction finally eliminates the possibility of recovering services formerly provided by that species.
 
3. It is often difficult to predict a priori how altered biodiversity will affect ecosystem services. Extinction or large declines of a harvested species clearly means loss of the direct benefits resulting from its exploitation. However, because of the complex web of interactions among species and the complexity of ecosystem processes, the precise impacts of biodiversity loss can be difficult to predict. For example, in the Northeastern U.S, habitat fragmentation and loss of predators can result in high densities of white-footed mice, which in turn have been linked to outbreaks of Lyme disease. Avoiding actions likely to adversely affect biodiversity and adjusting future management to incorporate knowledge gained from monitoring past actions will help to mitigate against unintended negative consequences of management choices.
 
4. Early implementation of strong measures to prevent biodiversity loss can improve chances of successful restoration later. Ecosystem restoration is an important component of current efforts to maintain ecosystem services, and should be supported. However, reversing the adverse effects of altered biodiversity has proven to be expensive and sometimes impossible when actions occur late in the process. Rehabilitating degraded ecosystems can only approximate former conditions and can be more expensive and difficult than protecting natural conditions and the services they provide at the outset. For example, government agencies spend millions of dollars annually to eradicate noxious invasive species because of the damage they cause to a variety of human enterprises. Similarly, substantial effort and money are invested in preventing extinction of those species listed as endangered by the Endangered Species Act. Early conservation action may avoid these expenses. In the end, when species become extinct, complete restoration is impossible.
 
*This statement was edited for a lay audience, with permission from the ESA.
D.U. Hooper 1*, F.S. Chapin III2, J.J. Ewel3, A. Hector4, P. Inchausti5, W.K. Lauenroth6, S. Lavorel7, D.M. Lodge8, M. Loreau9, S. Naeem10, B. Schmid4, H. Set?l?11, A.J. Symstad12, J. Vandermeer13, D.A. Wardle14,15
1 Department of Biology, Western Washington University, Bellingham, WA 98226 USA ; hooper@biol.wwu.edu
2 Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775 USA
3 Institute of Pacific Islands Forestry, Pacific Southwest Research Station, USDA Forest Service, 1151 Punchbowl St., Rm. 323, Honolulu, HI 96813 USA
4 Institute of Environmental Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057 Z?rich, Switzerland
5 Centre d’Etudes Biologiques de Chize, 79360 Villiers-en-Bois, France
6 Department of Forest, Rangeland, and Watershed Stewardship, Colorado State University, Fort Collins, CO 80523 USA
7 Laboratoire d’Ecologie Alpine, CNRS UMR 5553, Universit? J. Fourier, BP 53, 38041 Grenoble Cedex 9, France
8 Department of Biological Sciences, P.O. Box 369, University of Notre Dame, Notre Dame, IN 46556-0369 USA
9 Laboratoire d’Ecologie, UMR 7625, Ecole Normale Sup?rieure, 46 rue d’Ulm, F-75230 Paris Cedex 05, France
10 Department of Ecology, Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, New York, NY 10027, USA
11 University of Jyvaskyla, Department of Biological and Environmental Science, P.O. Box 35 (YAC), Fin-40351 Jyvaskyla, Finland
12 U.S. Geological Survey, Mount Rushmore National Memorial, 13000 Highway 244, Keystone, SD 57751 USA
13 Department of Biology, University of Michigan, Ann Arbor, MI 48109 USA
14 Landcare Research, P. O. Box 69, Lincoln, New Zealand
15 Department of Forest Vegetation Ecology, Swedish University of Agricultural Sciences, SE901-83, Ume?, Sweden
1 Ecosystem processes are natural flows of energy and matter, such as uptake and release of carbon dioxide and nutrients by plants and soil organisms during photosynthesis and decomposition, consumption of plants and animals by predators in ecosystem food webs, and the flow of water through soils and streams and into the atmosphere. Ecosystem goods such as food, construction materials, medicines, wild types for plant and animal breeding, genes for gene products in biotechnology, and aesthetic landscapes for tourism and recreation, have direct market value. Ecosystem services directly or indirectly benefit people. They include the maintenance of water cycles, climate regulation, air and water purification, pollination and pest control for crop plants, and soil formation and fertility.
 
Originally posted in “On Eagles’  Wings” December 27th 2005