Biodiversity loss due to tropical forest fragmentation:conservation in a modified lan

This discussion topic submitted by Beth Krisko at 12:56 pm on 3/21/00. Additions were last made on Friday, May 17, 2002.


Clearing of tropical forests has created a highly modified landscape where remnant patches of native flora are set in a matrix of agricultural lands and urban-residential development (Turner 1996, Williams-Linera et al 1998, Holl 1999). Deforestation of tropical forests has been rapid and extensive; between 1981 and 1990, the total loss of natural tropical forests was 154 ha, cleared at a rate of nearly 1% per year (Whitmore 1997). The vast majority of clearing in Latin America is for agricultural purposes, including both grazing and cultivation (Holl 1999). Loss of biodiversity in the tropics is directly related to forest clearing, which decreases total habitat area (Dale et al 1994). However, the effect of deforestation, changing landscape pattern, also negatively impacts biodiversity. Fragmentation causes remnant vegetation patches to be situated in different positions in the landscape, varying in size, shape, isolation (Sunders et al. 1990), and time since excision from the continuous forest (Turner 1996). These factors, in turn, influence the biodiversity of a fragment, "and in a complex manner, the biodiversity of the collection of fragments that occupies the landscape" (Turner 1996, p. 201). Despite negative effects caused by fragmentation, conservation in the modified tropical landscape must asses individual forest fragment's contributions to the protection of biodiversity. Management regimes can then be established to control the effects of fragmentation, so that remnant patches successfully maintain their natural qualities. In addition to protecting the native flora within patches, ecological restorative efforts should be applied to matrix lands (Lamb 1997), therefore, creating better connectivity between them.

I. Introduction
II. Fragmentation inducesÖÖ
A. Edge effects-- Patch size and patch shape influences forest edge to interior ratio. The forest edge, itself, and the amount of edge interacting with anthropogenic clearing influence ecological structure of forest remnant.
1. microclimate-temperature, light availability (Kapos et al 1997, Saunders et al. 1991, Turner 1996, Turton 1997)
2. wind damage (Laurence 1997, Saunders et al. 1991)
B. Isolation (landscape configuration)
1. Habitat isolation-isolation may reduce immigration of fauna, influencing the species richness of tropical forest fragments (Turner et al. 1996)
2. Landscape configuration of isolated remnants influences seed dispersal (Harrison 1999)
2. Time since isolation-diversity is lost with increasing time since isolation (Saunders et al. 1991, Turner et al. 1996)
III. Conclusion
A. Summarization of fragmentation impacts on biodiversity
B. Translate relevant literature on fragmentation into applicable information for conservation in the modified tropical landscape (Lamb 1997)


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evidence. Journal of Applied Ecology 33: 200-209
Turton, S.M. and H.J. Freiburger. 1997 Edge and aspect effects on the mircroclimate of
small tropical forest remnant on the Atherton Tableland, Northeaster Aulstralia.
In: Laurence W.F. and Bierregaard, Jr., R.O. (Editors), Tropical forest remnants. The University of Chicago Press, Chicago.
Whitmore, T.C. 1997. Tropical forest disturbance, disappearance, and species loss, pp.
2-28. In: Laurence W.F. and Bierregaard, Jr., R.O. (Editors), Tropical forest
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Williams-Linera, G., V. Domiguez-Gastelu, and M.E. Garcia-Zurita. 1998.
Microenvironment and floristics of different edges in a fragmented tropical rainforest. Conservation Biology 12 (5): 1091-1102



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