An approach to management of natural resources that emphasizes how little is known about the dynamics of ecosystems and that, as more is learned, management will evolve and improve. Adaptive management is a systematic strategy that seeks to improve resource assessment, allocation, conservation, and maintenance by learning from management outcomes. Natural systems are very complex and dynamic, and human observations about natural processes are fragmentary and often inaccurate. Furthermore, much of the variability that affects natural populations is unpredictable and beyond human control. This combination of ignorance and unpredictability means that the ways in which ecosystems respond to human interventions are unknown and can be described only in probabilistic terms. Nonetheless, management decisions need to be made. Adaptive management proceeds despite this uncertainty by treating human interventions in natural systems as large-scale experiments from which more may be learned, leading to improved management in the future (Fig. 1). See also: Conservation of resources; Ecosystem; Environment; Environmental engineering

An ongoing current event in which a large number of living species are threatened with extinction or are going extinct because of environmentally destructive human activities. The Earth is presently in the midst of a mass extinction event. In the past, there have been five other similar large extinctions. Because of this, the current Anthropocene extinction is often referred to as the sixth extinction or the sixth great mass extinction; another term is the Holocene extinction because this event is taking place in the current Holocene Epoch, which covers the last 10,000 years of the Earth's history. However, as the present-day extinction event is anthropogenic (that is, related to or resulting from the influence of humans on nature), the favored term is Anthropocene extinction. This article presents an overview of the five previous large extinctions, the major human activities causing the Anthropocene extinction, and the trends in species extinction related to this present-day extinction event (see illustration). See also: Biodiversity; Endangered species; Extinction; Holocene; Mass extinctions; Paleobiodiversity; Paleoecology; Species concept

The application of ecological principles to the solution of human problems and the maintenance of a high quality of life. Applied ecology is a branch of ecology that applies concepts of ecology to address contemporary problems involving natural resources and human welfare. In general, humans are an integral part of ecological systems. Moreover, humans depend upon healthy, well-operating, and productive systems for their continued well-being. For these reasons, applied ecology is based on a knowledge of ecosystems and populations, and the principles and techniques of ecology are used to interpret and solve specific environmental problems and to plan new management systems in the biosphere (see illustration). Although a variety of management fields, such as forestry, agriculture, wildlife management, environmental engineering, and environmental design, are concerned with specific parts of the environment, applied ecology is unique in taking a view of whole systems, as well as attempting to account for all inputs to and outputs from the systems—and all impacts. See also: Biosphere; Ecological methods; Ecological modeling; Ecology; Ecosystem; Human ecology; Systems ecology

The cultivation of freshwater and marine species for human purposes. Aquaculture, or aquatic farming, is concerned with the raising of animals and the harvesting of plants in freshwater and marine environments (Fig. 1). In other words, it is the aquatic equivalent of land-based agriculture. When marine species are involved, aquaculture is often referred to as mariculture. The concept of aquaculture is not new, having begun in China about 4000 years ago, and the practice of fish culture there has been handed down through the generations. Today, aquaculture is a modern, multidisciplinary technology. Overall, aquaculture accounts for approximately half of the world's production of fish and shellfish, according to the Food and Agriculture Organization of the United Nations. See also: Agricultural science (animal); Agricultural science (plant); Agriculture; Fisheries ecology; Marine conservation; Marine ecology; Marine fisheries

The biological diversity of different plant and animal species living on the island of Borneo. Borneo is the third largest island in the world. Located in Southeast Asia and straddling the Equator, it is divided among three countries: Indonesia, Malaysia, and Brunei. The largest part of Borneo, comprising the southern and eastern parts of the island, is Indonesian territory and often referred to as Kalimantan, whereas the northern part belongs to Malaysia (the states of Sarawak and Sabah) and Brunei (Fig. 1). Ecologically, Borneo has a profusion of tropical rainforests and is one of the most important centers of biodiversity in the world, with numerous plant and animal species having evolved on and inhabiting the island. As such, the natural richness and biological diversity of Borneo have attracted scientists, and dozens of new species of plants and animals are being discovered annually. However, it takes much effort to uncover the natural secrets of the island because the interior of the island is a remote area that is difficult to reach. Most of it is very mountainous, and few inland roads exist. See also: Animal evolution; Biodiversity; East Indies; Ecological communities; Island biogeography; Oceanic islands as evolutionary laboratories; Plant evolution; Plant geography; Rainforest; Speciation; Zoogeography

Management of the human use of natural resources to provide the maximum benefit to current generations while maintaining capacity to meet the needs of future generations. Conservation includes both the protection and rational use of natural resources. In their attempts to protect and limit the use of the Earth's limited natural resources, environmentalists and conservationists must consider the preservation, restoration, beneficiation, maximization, reutilization, substitution, allocation, and integration of these resources. Another factor that plays a role in the use and conservation of natural resources is global climate change (global warming). In particular, humans are inadvertently altering the atmospheric chemical composition on a global scale, which has led to an unprecedented warming of the global atmosphere. This rapid warming is changing the biomes of the world, which in turn will affect the survival of all plant and animal species, including humans (Fig. 1). See also: Biome; Conservation of species; Environment; Environmental engineering; Environmental management; Global climate change; Global warming

The collective measures and actions concerned with the preservation and restoration of animal and plant species and their habitats. To conserve an endangered species, an adequate number of populations must be maintained within a sufficient amount of protected habitat, with the goal of minimizing the likelihood of future extinction. In fact, of the thousands of animal and plant species listed as threatened or endangered, the majority are declining as a result of the loss of habitat (Fig. 1). The most direct approach for ensuring that a species will continue to exist is to conserve its environment. The primary elements that determine the overall effectiveness of a habitat conservation measure are (1) the number and type of factors causing species decline; (2) the condition of the habitat and the surrounding land matrix; and (3) the specific regulatory and management approaches used on the land, which may not always directly relate to species conservation. Although a variety of land protection strategies are available for conserving endangered species, the most common is federal land management. Government agencies often have direct responsibility for ownership and management of lands containing endangered species, but there are a growing number of private initiatives that can also be successful in habitat protection. See also: Biodiversity; Conservation of resources; Endangered species; Environment; Environmental management; Extinction; Forestry; Land-use planning; Population ecology; Speciation; Species concept

The response of corals to environmental stress in which they eject the single-cell algae that live within the transparent coral tissue, making the white coral skeleton visible. Corals (Fig. 1) are animals that live in a partnership (symbiosis) with single-cell plants, specifically, a type of algae called zooxanthellae (genus Symbiodinium). These algae live inside the coral tissue and use sunlight to generate energy through photosynthesis, just as terrestrial (land) plants do. Zooxanthellae provide up to 90% of their coral host's energy requirements. This partnership enables corals to construct the calcium carbonate skeletons that form reefs up to thousands of kilometers/miles in extent. The complex three-dimensional structure of reefs provides habitat for a wide array of plants and animals, including as much as one-quarter of all ocean fish species. People also benefit from coral reefs; not only do coral reefs provide a supply of fish for human food consumption, but they also (1) protect coastlines from erosion by waves, (2) act as a source for compounds used in new drug discoveries and medical treatments, and (3) provide areas for tourism and related industries. See also: Algae; Coral reef structural complexity; Ecological communities; Ecosystem; Marine ecology; Mutualism; Photosynthesis; Reef; Symbiosis

Pathological conditions affecting the health of coral and causing its physiological dysfunction. Broadly defined, coral disease (Fig. 1) is any impairment to coral health resulting in physiological disturbance and breakdown. It usually involves three components: (1) the host, such as a coral; (2) an agent; and (3) the surrounding environment. Most agents are microbial and include bacteria, fungi, viruses, and protistans (single-celled organisms). The rise of coral diseases is probably a reaction to global sea warming, increased ultraviolet (UV) radiation, and runoff from land, including sewage, nutrients, and toxic chemicals (for example, pesticides and agrochemicals). Humans clearly are implicated in the problem; for example, pathogens in infected corals have been traced directly to human sewage. See also: Coral reef structural complexity; Disease; Ocean warming; Pathogen; Reef; Ultraviolet radiation (biology)

A measure of the three-dimensional structure of live coral communities on reefs. Coral reef structural complexity is an intrinsic element of coral reef ecosystems and quantitates the surface area of coral in relation to its linear area. The structural complexity of coral reefs is important because it provides information on the health of coral reefs and the species that inhabit the coral reef's ecological neighborhood. When a coral reef is threatened by any of a variety of causes [for example, coral bleaching (Fig. 1) or coral diseases], as is the present case in marine locations around the world, the whole community of organisms that resides within and around that coral reef will be at risk. Thus, conservation and restoration efforts must be instituted to ensure the future survival of all coral reef communities. See also: Conservation of resources; Conservation of species; Coral bleaching; Coral diseases; Ecological communities; Ecology; Ecosystem; Marine ecology; Reef; Restoration ecology