This is a problem as it can reduce their ability to respond to changing environmental factors or to new diseases or parasites. Another effect of fragmentation is the changes caused to the physical environment. Plants and animals are more likely to be exposed to what are known as 'edge effects'. As a block of forest becomes fragmented, there is an incease in the amount which is edge. Edge effects are numerous and include factors such as increased sunlight reaching the forest floor with associated drying effects.
Temperatures are consequently hotter and more variable, and humidity is lowered.
Increased wind shear results in greater numbers of fallen trees which further opens up the canopy. The changed environmental conditions cause changes to sensitive insect populations, and predatory behaviour by birds increases due to the more open canopy. These are just some of the direct effects of increasing the amount of edge. Most previous studies have focused on birds and mammals, and their responses at the community rather than individual level. To make statistically valid conclusions regarding individual species, you need large sample sizes.