The edge effects present in areas of fragmented forest are extremely detrimental to the area of forest they contain.
It leaves them more susceptible to external threats, and leaves the areas of forest left too small to support a
healthy biosystem. The best compromise we can make is to give suggestions about how to make fragmentation more
"healthy." We suggest you do that by trying to surround fragmented areas with secondary forest growth, or by
trying to use controlled logging around the edges of a particularly large chunk of rainforest.
Following information taken from:
Soule, Michael; Orians, Gordan. Conservation
. Washington: Island Press, 2001.
There was a forest fragmentation experiment in Manaus
Brazil, here are some examples of the results:
- overall reduction in biomass
- reduction of overstory vegetation
- increase in understory vegetation
- fragment edges were hotter, drier,
- high mortality
of trees at edges
- higher leaf-fall
rate near edges
- air temperature, litter biomass and
moisture, and percentage of ground covered with twigs were correlated with
from the edges
- beetle species composition changed
both with decreasing distance from the edge, and with decreasing fragment
Critical Area due to Fragmentation
There is no critical area.
In the Lovejoy experiment at Manuas, documented effects were:
2 years - Large flocks of mixed species birds disappear in both the 1 and 10 hectare square plots
10 years- After 10 years, all animals with very large ranges (army ants, bird flocks that follow army ants, and animals like
capuchin monkeys) had completely disappeared from even a 100 hectare square.
How to Mitigate the Effects of Fragmentation :
Fragmented areas surrounded by secondary forest growth were healthier than areas surrounded by shrub or grass.