Showing papers by "Luke Parry published in 2007"

Quantifying the biodiversity value of tropical primary, secondary, and plantation forests.

Abstract: Biodiversity loss from deforestation may be partly offset by the expansion of secondary forests and plantation forestry in the tropics. However, our current knowledge of the value of these habitats for biodiversity conservation is limited to very few taxa, and many studies are severely confounded by methodological shortcomings. We examined the conservation value of tropical primary, secondary, and plantation forests for 15 taxonomic groups using a robust and replicated sample design that minimized edge effects. Different taxa varied markedly in their response to patterns of land use in terms of species richness and the percentage of species restricted to primary forest (varying from 5% to 57%), yet almost all between-forest comparisons showed marked differences in community structure and composition. Cross-taxon congruence in response patterns was very weak when evaluated using abundance or species richness data, but much stronger when using metrics based upon community similarity. Our results show that, whereas the biodiversity indicator group concept may hold some validity for several taxa that are frequently sampled (such as birds and fruit-feeding butterflies), it fails for those exhibiting highly idiosyncratic responses to tropical land-use change (including highly vagile species groups such as bats and orchid bees), highlighting the problems associated with quantifying the biodiversity value of anthropogenic habitats. Finally, although we show that areas of native regeneration and exotic tree plantations can provide complementary conservation services, we also provide clear empirical evidence demonstrating the irreplaceable value of primary forests.

Predicting the Uncertain Future of Tropical Forest Species in a Data Vacuum

Abstract: WHEN SUPPORTED BY SUFFICIENT EVIDENCE, predictive analyses and scenario building can make important contributions towards devising conservation policy strategies. Wright and Muller-Landau (2006a, henceforth termed WMLa) provide a timely analysis that attempts to predict the future of tropical forest species based on human population-driven projections of tropical deforestation. Citing evidence of slowing population growth and rapid urbanization they suggest that deforestation rates are expected to decrease, and natural forest regeneration through secondary succession to accelerate. WMLa use their predictions of an increase in secondary forest area to paint an optimistic picture of the future, going so far as to suggest that the widely anticipated mass extinction of tropical forest species will be avoided (see also Aide & Grau 2004). Brook et al. (2006, henceforth termed BBKS) reject the optimistic predictions of WMLa by reinforcing the importance of a number of original caveats made by WMLa, as well as raising additional objections. BBKS indicate that the relationship between rural and urban population growth and deforestation is too complex to be reliably predicted. They also argue that the negative effects of the heavy momentum set in motion by current patterns of deforestation and population growth (i.e., loss of irreplaceable primary source habitat, e.g., Brooks et al. 2002, Brook et al. 2003, and extinction debt, Tilman et al. 1994) are irreversible before future reductions in deforestation rates are able to rescue committed extinctions. Despite this criticism Wright and Muller-Landau (2006b, henceforth WMLb) retain confidence in their optimistic projection, arguing that their simulations were robust to variability in the growth of urban versus rural human populations projected by the FAO, which already take into account existing biases in age structure. However, in addition to assumptions regarding human demography and the fate of undisturbed primary forests, the predictions of WMLa rely centrally upon net changes in forest cover and the (explicit) assumption that all types of forest cover can be treated equally—specifically that primary, secondary, and degraded forests can be considered to have similar ecological value. Citing a single key

Large-vertebrate assemblages of primary and secondary forests in the Brazilian Amazon

Abstract: Secondary forests account for 40% of all tropical forests yet little is known regarding their suitability as habitat for diurnal large mammals and game birds This is especially so for second-growth that develops on large areas of degraded land We address this by investigating assemblages of large-bodied birds and mammals in extensive patches of secondary forest in the Jari region of the north-eastern Brazilian Amazon, comparing species richness and abundance against that of adjacent undisturbed primary forests We conducted 184 km of line-transect censuses over a period of 3 mo, and found that although primary and secondary forests held a similar abundance of large vertebrates, the species composition was very different Secondary forests supported a high abundance of ungulate browsers (085 vs 044 indiv per 10 km) and smaller-bodied primates (156 vs 46 indiv per 10 km) compared with primary forests However, large prehensile-tailed primates were absent (black spider monkey Ateles paniscus) or at very low abundance (Guyanan red howler monkey Alouatta macconelli) in secondary forest The abundance of large frugivorous/granivorous birds was also low in secondary forests compared with primary forests (226 vs 371 individuals per 10 km, respectively) Faunal assemblages appear to reflect food resource availability Concurrent vegetation surveys indicated that secondary forests had high levels of terrestrial and understorey browse Fruit production was largely restricted to pioneer trees such as Bellucia and Inga spp Although these regenerating forests were an important habitat for large mammals and birds, they were limited in terms of faunal richness, particularly dispersers of large-seeded plants