Forest fragmentation and biodiversity: the case for intermediate-sized conservation areas

Abstract

Understanding the effects of forest fragmentation on biodiversity is essential for successful and efficient forest conservation. Four factors may cause loss of biodiversity in forest fragments: the effect of non-random sampling of the original forest, reduced forest size, isolation and edge effects. A review of 58 papers on effects of forest fragmentation reveals that general conclusions from fragmentation research are biased due to a focus on birds, on size-effects rather than isolation, and on species presence rather than population sizes. Perhaps the most important finding is that current knowledge on fragmentation effects is based mainly on studies in small fragments (<10 ha). These are dominated by edge effects, can not contain viable populations for many species and are rarely the focus of conservation programmes. Studies of small fragments can not be extrapolated to largersized, protected areas, and do not necessarily support the case for needing extremely large, protected areas. Conservation of medium-sized, strategically-located areas may be a more efficient option for biodiversity conservation, given financial, social and logistic limitations. More research is needed on forest fragments that arc representative of the sizes of real-world protected areas (i.e. >10 000-100 000 ha) and should focus on the biological and human-induced processes which determine species persistence.

Efeitos de borda sobre a vegetação e estruturação populacional em fragmentos de Cerradão no Sudoeste Goiano, Brasil

“…Para fragmentos de mesma forma, a relação área/perímetro é maior quanto maiores são os fragmentos e, portanto, quanto maior esta relação menor a intensidade dos efeitos de borda (Zudeima et al 1996). Os fragmentos menores podem ser totalmente devastados por ventos fortes, enquanto que em fragmentos maiores podem ocorrer perturbações iniciais e posteriormente, estabelecimento de vegetação secundária em locais próximos às suas bordas (Gascon et al 2000;Laurance et al 2002).…”

Mediating Forest Transitions: ′Grand Design′ or ′Muddling Through′

“…The fate of much biodiversity will depend upon landscape mosaics where only small areas are totally protected (e.g. Zuidema et al 1997;Vandermeer & Perfecto 2007). Many of these landscapes will be under decentralised management regimes driven by local civil society (Glück et al 2005).…”

“…As global public goods they should receive international financing to pay any opportunity costs of local communities. But, in view of the limitations of such financing and the current extent of existing PAs, these special areas are likely to be a relatively small core of conservation landscapes (Zuidema et al 1997). We must, therefore, accept flexibility so that landscapes might adapt in a variety of ways to changes in economic opportunities, climate and societal values.…”

Ecologia da paisagem de remanescentes florestais na bacia hidrográfica do Ribeirão das Pedras - Campinas -SP

“…A abrangência da borda é função do formato do fragmento, ou seja, quanto mais próximo da forma circular, menor a borda do fragmento, portanto menor será sua suscetibilidade às perturbações externas (ZUDEIMA, 1996).…”