Revista Chilena de Historia Natural 78 (3): 451-467, 2005
RESEARCH ARTICLE
A quantitative analysis of forest fragmentation in Los Tuxtlas, southeast Mexico: patterns and
implications for conservation
Habitat loss is a critical threat to tropical biodiversity and its quantification constitutes a
central conservation issue. Typically, assessments have been based on deforestation rates statistics. However, this overlooks the
effects brought about by the spatial reconfiguration of the remaining habitat: fragmentation. We present an analysis of fragmentation in
a Neotropical site aimed at: (a) devising a protocol for its quantification, (b) using such protocol to provide insights on the ecological
consequences of fragmentation, (c) exploring its applicability to address the hypothesis that forest size inequality decreases with
elevation, an indicator of habitat accessibility. We applied the Gini coefficient (G) and the Lorenz curve to analyze fragment-size
variation using a satellite-generated map. We also estimated edge effect, fragment shape and isolation. Remaining forest includes
1,005 fragments, ranging from 0.5 to 9.356 ha (median = 0.89). Size inequality was very high (G = 0.928), producing a flattened Lorenz
curve. Forty percent of the fragments did not maintain an area free of a 30-m edge effect, and larger fragments showed a marked
deviation from ideal circular forms. Eighty-four percent of the fragments lay further than 500 m from the largest forest tract and their
size decreased with distance. Fragment size distribution changed with altitude: the Gini coefficient was lowest and forest coverage
was greatest at the highest altitude, but inequality peaked at an intermediate elevation. Given the current pace of habitat deterioration,
application of similar analyses may improve global assessments of tropical ecosystems and their perspectives for biodiversity
conservation.
Key words:
edge effect, fragment
shape, Gini coefficient, Lorenz curve, tropical rain forest
