Tropical forest loss impoverishes arboreal mammal assemblages by increasing tree canopy openness.

Landscape-scale deforestation poses a major threat to global biodiversity, not only because it limits habitat availability, but also because it can drive the degradation of the remaining habitat. However, the multiple pathways by which deforestation directly and indirectly affects wildlife remain poorly understood, especially for elusive forest-dependent species such as arboreal mammals. Using structural equation models, we assessed the direct and indirect effects of landscape forest loss on arboreal mammal assemblages in the Lacandona rainforest, Mexico. We placed camera traps in 100 canopy trees, and assessed the direct effect of forest cover and their indirect effects via changes in tree basal area and canopy openness on the abundance and diversity (i.e., species richness and exponential of Shannon entropy) of arboreal mammals. We found that forest loss had negative indirect effects on mammal richness through the increase of tree canopy openness. This could be related to the fact that canopy openness is usually inversely related to resource availability and canopy connectivity for arboreal mammals. Furthermore, independently of forest loss, the abundance and richness of arboreal mammals was positively related to tree basal area, which is typically higher in old-growth forests. Thus, our findings suggest that arboreal mammals generally prefer old-growth vegetation with relatively low canopy openness and high tree basal area. However, unexpectedly, forest loss was directly and positively related to the abundance and richness of mammals, probably due to a crowding effect, a reasonable possibility given the relatively short history (~40 years) of deforestation in the study region. Conversely, the Shannon diversity was not affected by the predictors we evaluated, suggesting that rare mammals (not the common species) are the ones most affected by these changes. All in all, our findings emphasize that conservation measures ought to focus on increasing forest cover in the landscape, and preventing the loss of large trees in the remaining forest patches.

Tropical montane cloud forests: current threats and opportunities for their conservation and sustainable management in Mexico.

Tropical montane cloud forests (TMCF) are among the most threatened ecosystems globally in spite of their high strategic value for sustainable development due to the key role played by these forests in hydrological cycle maintenance and as reservoirs of endemic biodiversity. Resources for effective conservation and management programs are rarely sufficient, and criteria must be applied to prioritize TMCF for conservation action. This paper reports a priority analysis of the 13 main regions of TMCF distribution in Mexico, based on four criteria: (1) forest quality, (2) threats to forest permanence, (3) threats to forest integrity, and (4) opportunities for conservation. Due to the diverse socio-environmental conditions of the local communities living in Mexican TMCF regions, their associated social characteristics were also evaluated to provide a background for the planning of conservation actions. A set of indicators was defined for the measurement of each criterion. To assign priority values for subregions within each main region, an international team of 40 participants evaluated all the indicators using multicriteria decision-making analysis. This procedure enabled the identification of 15 subregions of critical priority, 17 of high priority, and 10 of medium priority; three more were not analysed due to lack of information. The evaluation revealed a number of subjects that had hitherto been undetected and that may prove useful for prioritization efforts in other regions where TMCF is similarly documented and faces equally severe threats. Based on this analysis, key recommendations are outlined to advance conservation objectives in those TMCF areas that are subjected to high pressure on forest resources.

Comparing the success of active and passive restoration in a tropical cloud forest landscape: A multi-taxa fauna approach.

Tropical forest restoration initiatives are becoming more frequent worldwide in an effort to mitigate biodiversity loss and ecosystems degradation. However, there is little consensus on whether an active or a passive restoration strategy is more successful for recovering biodiversity because few studies make adequate comparisons. Furthermore, studies on animal responses to restoration are scarce compared to those on plants, and those that assess faunal recovery often focus on a single taxon, limiting the generalization of results. We assessed the success of active (native mixed-species plantations) and passive (natural regeneration) tropical cloud forest restoration strategies based on the responses of three animal taxa: amphibians, ants, and dung beetles. We compared community attributes of these three taxa in a 23-year-old active restoration forest, a 23-year-old passive restoration forest, a cattle pasture, and a mature forest, with emphasis on forest-specialist species. We also evaluated the relationship between faunal recovery and environmental variables. For all taxa, we found that recovery of species richness and composition were similar in active and passive restoration sites. However, recovery of forest specialists was enhanced through active restoration. For both forests under restoration, similarity in species composition of all faunal groups was 60-70% with respect to the reference ecosystem due to a replacement of generalist species by forest-specialist species. The recovery of faunal communities was mainly associated with canopy and leaf litter covers. We recommend implementing active restoration using mixed plantations of native tree species and, whenever possible, selecting sites close to mature forest to accelerate the recovery of tropical cloud forest biodiversity. As active restoration is more expensive than passive restoration, both strategies might be used in a complementary manner at the landscape level to compensate for high implementation costs.