DESIGNING A PROTECTED AREA SYSTEM (PAS) III:
HABITAT CORRIDORS AND HUMAN FACTORS
Habitat Corridors
One way to overcome the problems of habitat fragmentation is to connect isolated habitat fragments with corridors along which plants and animals can migrate between fragments. The advantages of corridors are:
i) Populations of species becoming extirpated in one fragment can be re-established by immigration of the same species from extant populations in other fragments.
ii) Corridors allow genetic mixing between populations in different fragments, reducing the risks of inbreeding.
iii) Corridors allow natural seasonal or diurnal migrations to occur (e.g. annual migrations of herbivores between wet season and dry season habitats; daily movements of birds between feeding and roosting sites etc.).
The problems with corridors are:
i) Corridors are thin and edge effects are high. A forest corridor, for example, would favour species which live along the edges of forests. Species which prefer to live in the forest interior would probably not use it. To avoid this effect, corridors should be as wide as is feasible.
ii) Corridors can help movement of pests and diseases between habitat patches.
iii) Corridors can allow fire to spread from one habitat patch to another.
iv) Corridors are very easily affected by human disturbance. They are easily interrupted or cut by human activities and if large vertebrates are using them for migration, those animals are easily hunted. In this way badly designed corridors can act as a death trap - attracting animals away from their habitat, exposing them to danger and not delivering them safely to another safe patch of habitat.
How wide should the corridor be?
This depends on the animals likely to use the corridor. For insects and small birds, a single line of trees connecting two forest patches may be sufficient to allow them to move from one patch to another. For small mammals a width of a few hundred metres up to 2-3 km is sufficient, but for large mammals a minimum width of 10-20 km is necessary.
Corridors of vegetation along river banks make particularly effective wildlife corridors - so called RIPARIAN STRIPS. They serve as refuges for wildlife during the dry season and they can connect upland with lowland habitats in mountainous areas, thus providing for elevational migrations.
Buffer Zones
Conflicts often occur at the edges of PA's where wildlife habitats meet land used intensively by humans (e.g. agriculture, urban areas etc.). To reduce such conflicts buffers zones are created surrounding core areas of strictly protected habitat. A buffer zone is an area of mainly natural habitat, where some forms of human use, compatible with protection of the core area, are allowed. Such activities can include some timber harvesting, hunting, gathering of non-timber forest products, eco-tourism etc., but the basic habitat structure should be retained. Buffer zones should be less attractive to wildlife than the core areas, so that animals entering buffer zones tend to return to the core areas, rather than migrating out into developed areas. Buffer zones help protect people from wildlife and protect wildlife from people.
Hydrological Criteria
In some areas, protection of water resources, not wildlife, is the top priority, although watershed protection areas also benefit wildlife. The need for protection of a watershed depends on:
i) Susceptibility to flooding - which is determined by rain intensity and frequency, soil texture, steepness and length of slopes.
ii) History of flooding - areas with frequent flooding should receive the highest priority for watershed protection.
iii) Streams becoming more seasonal - streams which used to be permanent but which now flow only in the rainy season are a danger sign, warning that the forest in the watershed should be restored and protected.
iv) Socioeconomic Importance - this depends on the number of people that live in the watershed and the area and value of agricultural land in the watershed.
Tourism Criteria
Tourism plays an important part in the economy of many developing countries and the tourism potential of an area should be included in the selection process, once biological factors have been considered. e.g.
Is the area accessible?
Does the area have "star" wildlife species?
Are the animals easily seen?
Is the area scenically attractive?
Does the area also have cultural interest?
Does the area also have other recreational attractions e.g. beaches, waterfalls, etc.?
Is the area close to other tourist attractions?
Political, Social and Economic Criteria
In theory biological criteria such as species diversity and endemism etc. should determine whether or not an area is protected but in reality this is often determined by political or economic factors.
e.g.…
Is legislation adequate to protect the area? Can the government legally prevent businessmen developing the area? Does the government own the land?
Is the budget large enough? It's no good declaring an area protected, if there is no money to actually protect the area. Money is needed for guards, vehicles and radios etc.
Participation of local people
Unless local people support the creation of a PA, it will fail. Local people must be educated as to the value of the protected area. They must be involved in its creation and management. They should be employed as Forestry Department staff in the area. They should also benefit economically from tourists visiting the protected area e.g. by providing accommodation or food or by acting as guides.