|Basic Concepts in Environment, Agriculture and Natural Resources Management: An Information Kit (IIRR, 1993, 151 p.)|
Habitat and niche
Habitat = address or home of an organism
· The area where an animal lives or its home, usually an ecosystem or an area within an ecosystem.
· Habitat relates mostly to the non-living physical or chemical conditions of the area such as temperature, rainfall, salinity, sunlight, soil and elevation.
· Habitat and the preservation of biodiversity
· Habitat conservation is directly related to species conservation. The protection of habitats is a more systematic and comprehensive way or preserving species. By protecting any given habitat, a host of species will automatically be protected. This is often more useful than trying to preserve a single species. The loss of habitat is the main cause of species loss in the world. For example, the preservation of mangrove habitat protects those plants and animals that are associated with it.
Niche = occupation of an organism in its community
· A species niche is composed of its habitat, plus the biological or living things found the habitat. The living component (plants and animals) of a habitat is called a community.
· Biological factors include location on the food chain (producers, herbivores, carnivores, etc.) predator/prey relationships and reproductive requirements.
· Interrelationships and interactions are important aspects of niche. For example, tall trees provide shade for plants and animals living under it; birds help disperse seeds of certain trees; and, worms help to aerate the soil.
· Temporal activities are also important in understanding niche. Activities which relate to temporal cycles such as day and night, lunar or seasonal cycles help to define the niche of an organism.
Specialized is generalized niches
Specialized niches apply to species which have very well-defined or narrow physical, biological or chemical requirements for survival. If an organism can only be found within very limited or specific conditions, it is considered to have a very specialized niche. The dugong is an example of an animal with a specialized niche. It requires seagrass beds for food and warm, calm waters for rearing its young. Animals such as the dugong with a specialized niche are more susceptible to extinction than animals with a generalized niche.
Generalized niches apply to species which can exist in a broad range of conditions. Humans are the best examples of species with a generalized niche. In the Philippines, as elsewhere, humans live in diverse conditions with an almost infinite variety of interrelationships. Other animals that are considered to have generalized niches are cockroaches, flies and rats.
Competitive exclusion principle
The fact that no two species can occupy the same niche is called the competitive exclusion principle. For example, two different species of Kingfisher may share the same habitat but may feed on different organisms at different times of the day or in different places.
Niche and ecosystems changes
Understanding the niche of species within an ecosystem will provide insights as to what the consequences of change may be. Two of the more common changes are the elimination of a species and the introduction of exotic or foreign species. The removal of a species whether through extinction or habitat loss can have many undesirable effects. This is often seen when pesticides eliminate beneficial as well as harmful insects. The result can be the removal of an important predator of harmful insects and subsequent increases in the pest population. Understanding the niche of the various organisms in a given habitat will help to predict potential effects of change. The introduction of exotic or non-native species can also bring about detrimental effects. If the introduced species is known to be very resilient and competitive and has a generalized niche, it may colonize-large areas to the detriment of native species. The Eurasian Tree Sparrow is an example of this in the Philippines.