Efeitos da fragmentação florestal sobre as comunidades de aves

Abstract

RESUMO.Este trabalho discute os efeitos da fragmentação florestal sobre as comunidades de aves verificados em diversos estudos, e apresenta considerações para a conservação da avifauna. Os principais fatores ambientais determinantes da riqueza de aves em florestas e que são alterados no processo de fragmentação são a área florestal, o grau de isolamento, a diversidade de hábitats e o efeito de borda. Os diversos estudos diferiram em seus resultados em relação aos efeitos da fragmentação sobre a avifauna, mas alguns padrões são notáveis: 1. extinção seletiva de espécies nos fragmentos (há grupos mais susceptíveis ou mais resistentes ao processo, enquanto outros são até beneficiados); 2. densidade compensatória (aumento na densidade de algumas espécies em relação a sua densidade em florestas contínuas). Os resultados levam à conclusão de que para uma plena conservação da comunidade de aves florestais de uma região é necessária a conservação das grandes florestas, ao invés de diversos fragmentos pequenos.Palavras-chave: aves, biogeografia de ilhas, conservação, fragmentos florestais, SLOSS. ABSTRACT. Effects of forest fragmentation on bird communities.Effects of forest fragmentation on bird communities and considerations for avifauna conservation are discussed here. Forest area, isolation, habitat diversity, and edge effect are the main environmental factors that determine bird richness in forests, and they undergo alterations during forest fragmentation. Several studies have shown different results regarding to fragmentation effects on the avifauna, and some of them are noticeable, such as: (1) selective extinction within the fragments, i. e., some groups are more susceptible than others to the process and some other groups are even benefited by fragmentation; (2) compensatory density, meaning that there is a density increase of some species in relation to their density in continuous forests. It has been enforced that it is necessary to preserve large extensions of forests instead of preserving several small fragments.

Caracterização da Cobertura Florestal de Unidades de Conservação da Mata Atlântica

“…Já no MONA Encontro dos Três Rios os seis fragmentos existentes se dividiram igualmente entre as classes centrais. Assim, os dados demostram que um número expressivo de remanescentes florestais das unidades de conservação de Três Rios apresenta forma alongada ou irregular, o que pode comprometer a conservação da biodiversidade na região (Saunders et al, 1991;Gimenes & Anjos, 2003;Laurance & Vasconcelos, 2009). …”

Avifauna from a campus of Universidade Estadual do Centro-Oeste, Guarapuava, Paraná State, Brazil

“…Currently, several researches have been conducted mainly in natural and modified areas situated close or in the dependences of universities (campi), as observed in Monteiro and Brandão (1995) and Philippsen et al (2010). These areas commonly are urban and suburban zones comprising or not natural fragments (VOTTO et al, 2006) and studies regarding fragmentation effects in those areas have increasied ANJOS, 2003). In Paraná State, new ornithological contributions were performed in forest remnants such as Galina and Gimenes (2006), Lopes and Anjos (2006) and Philippsen et al (2010).…”

“…Furthermore, forest remnants may reduce the extinction rate of some species. Some natural populations may be structured in differentiated patterns, with extinction and recolonization cycles, compounding a mosaic of temporal populations interconnected by different migration degrees among them (HANSKY et al, 1996). For some species, all populations become ephemeral with distribution among forest remnants changing along the course of time.…”

“…As an effect of the chaotic urban development, several bird species inhabiting forest fragments are exposed to ecological processes that affect their dependence relationship to the fragment. This relationship varies according to environmental traits and intrinsic species characteristics (GIMENES; ANJOS, 2003;VIANA et al, 1997;WARBURTON, 1997). Nevertheless, birds occurring in these locations generally represent new colonizations, since these areas are usually reforestation locations with strong human interference on composition and structure of the vegetation (ANJOS; LAROCA, 1989;KRÜGEL;ANJOS, 2000).…”

“…Small fragments tend to be similar in fauna composition, sustaining those species more adapted to modified habitats. Small forest remnants are inclined to not be self-sustainable increasing the extinction chance of some species throughout time ANJOS, 2003;VIANA et al, 1997).…”