Although the researchers considered human disturbance as a possible cause for this loss of biodiversity, they consider it much more probable that the main contributing factors are those related to isolation. The extinction consists of death of individuals and failure of new recruitment (often due to uneven competition). The latter result is evident in the finding that some areas of the fragment resembled logged forest in which climbers had taken over (possibly due to increased light penetration). They found that in this particular fragment, forest structure and floristic composition were similar in the periphery and the center of the fragment. The researchers also note that fragments can act as refuges for species for long (but not indefinite) periods of time.

Data from fragments of the Atlantic rain forest of Brazil:

Researchers studied geographical characteristics of 1839 forest fragments in an area of 623 km^2 (which were in the final stage of fragmentation) surrounded by sugar-cane fields in the Atlantic rain forest of Brazil. They found that in general the fragments were small and close together.

They analyzed the fragments by degree of isolation, edge effects and shape using GIS software. They grouped the fragments based on the distance (d) from one fragment to another for d = 50m, 75m, 100m, 150m, 250m, and 350m.  For d = 50m, there were 1580 groups which contained 49% of the total forest area, for d = 250m, the groups contained 95% of forest area, and for d = 350m, 98% was included. Some fragments acted as important bridges or stepping stones between blocks of fragments.

The researchers discussed the geographical characteristics of the fragments in the context of island biogeography theory, which states that:

one large reserve is better than one small one
one large reserve is better than several small ones of equal total area (because the latter has a higher proportion of edge zone)
fragments close together are better than those that are far apart for species survival
corridors help improve species survival and biodiversity
round reserves are better than reserves of other shapes
They found that the habitat type of the matrix is important for dispersing species (thus we could reforest uninhabitable matrix to reduce isolation of populations). Additionally, they found that in simulations, reforestation of fields between the fragments resulted in an increase of forest area by 48% and an increase in interior area by 166%.

They recommend protection of large fragments, reforestation to connect fragments, and second-growth forest to improve the matrix.

1.