1. Edge effects
If you are a plant or animal living in a
small natural area, you are never far away from the boundary fence. Your neighbours’ actions can have a severe impact on you. Some pressures include:
littering and dumping, noise, bright lights at night, storm-water run-off,
fertilizer and pesticides, alien plants and animals, damage to fences and
2. Broken food chains
Small, isolated natural areas are often
unable to support all the plants and animals that make up that ecosystem’s
food chains and food webs. Sometimes predators like snakes or caracals are
killed because people think they are a threat. When the predators are gone,
natural areas can become degraded because there is nothing to control the
numbers of herbivores, which can then destroy the vegetation.
3. Unsuccessful breeding
In small natural areas there may be too few individuals for breeding to take place successfully. When the breeding population gets very small, in-breeding may eventually weaken the population. This happens because there is not enough genetic diversity to allow the population to adapt to changes (e.g. disease, climate change).
At breeding time, many animals (e.g. leopard toads)
are killed on the roads as they move from one small natural area or garden
to a wetland in search of a mate. Some plants depend on a single type of insect to
pollinate their flowers so that they can make seeds. If the pollinator
disappears from the area, the plant will not be able to reproduce.
4. Nowhere to go
Before natural areas became fragmented, plants and animals were able to move much more freely than they can today. When there was a drought or fire, animals could migrate to places where food and water were available.
Today we are starting to experience the effects of
climate change. Plants, animals and people may need to move to places where
the temperature and rainfall are more suitable. Fragmentation will make it
difficult for plants and animals to move to places with suitable climates.
This may increase the rates of extinction.
5. A challenge to manage
Small natural areas are expensive to manage because you need more staff to manage many small areas than a few large areas. Small natural areas also experience many pressures from neighbours.
It is difficult to manage natural areas in a city
or town. For example, people don’t like bush fires close to their homes, but
fynbos needs to burn occasionally in order to survive.