Habitat Specificity Modulates the Response of Small Mammals to Habitat Fragmentation, Loss, and Quality in a Neotropical Savanna

Landscape conversion of natural environments into agriculture and pasture are driving a marked biodiversity decline in the tropics. Consequences of fragmentation might depend upon habitat amount in the landscape, while the quality of remnants can also affect some species. These factors have been poorly studied in relation to different spatial scales. Furthermore, the impacts of these human-driven alterations may go beyond species loss, possibly causing a loss of ecosystem function and services. In this study, we investigated how changes in landscape configuration (patch size and isolation), habitat loss (considering a landscape gradient of 10, 25, and 40% of remnant forest cover), and habitat quality (forest structure) affect small mammal abundance, richness, taxonomic/functional diversity, and species composition in fragmented landscapes of semideciduous forests in the Brazilian Cerrado. Analyses were performed separately for habitat generalists and forest specialists. We live-trapped small mammals and measured habitat quality descriptors four times in 36 forest patches over the years 2018 and 2019, encompassing both rainy and dry seasons, with a total capture effort of 45,120 trap-nights. Regression analyses indicated that the effect of landscape configuration was not dependent on the proportion of habitat amount in the landscape to determine small mammal assemblages. However, both patch size and habitat loss impacted different aspects of the assemblages in distinct ways. Smaller patches were mainly linked to an overall increase in small mammal abundance, while the abundance of habitat generalists was also negatively affected by habitat amount. Generalist species richness was determined by the proportion of habitat amount in the landscape. Specialist richness was influenced by patch forest quality only, suggesting that species with more demanding habitat requirements might respond to fragmentation and habitat loss at finer scales. Taxonomic or functional diversity were not influenced by landscape structure or habitat quality. However, patch size and habitat amount in the landscape were the major drivers of change in small mammal species composition in semideciduous forests in the Brazilian savanna.

Drought-induced Forest Dieback Increases Taxonomic and Functional Diversity But Not Phylogenetic Diversity of Saproxylic Beetles at Both Local and Landscape Scales

Context: Forest ecosystems worldwide are facing increasing drought-induced dieback, causing mortality patches across the landscape at multiple scales. This increases the supply of biological legacies and differentially affects forest insect communities.Objectives: We analysed the relative effects of local- and landscape-level dieback on local saproxylic beetle assemblages. We assessed how classic concepts in spatial ecology (e.g. habitat-amount and habitat-patch hypotheses) are involved in relationships between multi-scale spatial patterns of available resources and local communities.Methods: We sampled saproxylic beetle assemblages in commercial fir forests in the French highlands. Through automatic aerial mapping, we used dead tree crowns to assess dieback levels at several nested spatial scales. We analysed beetle taxonomic, phylogenetic and functional diversity related to differing levels of multi-scale dieback.Results: In line with the habitat-amount hypothesis, taxonomic and functional diversity, but not phylogenetic diversity, of beetle assemblages significantly benefitted from forest dieback, at both local and landscape scales. Very few single or interaction effects were detected in the multiplicative models combining local and landscape variables, though a significant positive effect of landscape-scale dieback on the abundance of cavity- and fungus-dwelling species was consistent with a spill-over effect. Increased landscape-scale dieback also caused a functional specialisation of beetle assemblages, favouring those related to large-diameter, well-decayed deadwood.Conclusions: Increasing tree mortality under benign neglect provides conservation benefits by heterogenising the forest landscape and enhancing deadwood habitats. Legacy retention practices could take advantage of unharvested, declining forest stands to promote species richness and functional diversity within conventionally managed forest landscapes.

Matrix condition mitigates the effects of habitat fragmentation on species extinction risk

Habitat loss is the leading cause of global biodiversity decline, but the influence of human pressure within the matrix surrounding habitat fragments remains poorly understood. Here we measure the relationship between fragmentation, matrix condition (measured as the extent of high human footprint levels), and the change in extinction risk of 4,327 terrestrial mammals. We find that the matrix condition and the fragmentation of habitat are strongly associated with changes in species extinction risk. Importantly, we discover that fragmentation is a stronger predictor of risk than species life-history traits, habitat loss, and habitat amount. Moreover, the importance of fragmentation increases with an increasing deterioration of the matrix condition, highlighting the critical influence matrix quality plays on the effects of fragmentation. These findings suggest that restoration measures in habitat matrices may be an important conservation action for mitigating the effects of fragmentation relative to extinction risk of terrestrial mammals.

Estimating landscape structure effects on pollination for management of agricultural landscapes

The present study aims to examine the effects of habitat fragmentation to find a pattern of forest patches in agricultural landscapes that provide the highest pollination level. For this purpose, using simulated agricultural landscapes, including different forest proportions and degrees of fragmentation, pollination in different scenarios was estimated. We used landscape metrics to measure the landscape composition and configuration of each simulated landscape and estimated their statistical relationship with pollination. Our results showed that the effects of fragmentation on pollination were affected by two significant factors; 1- habitat amount and 2- small patches' capacity to supply pollination. Our results showed that when small patches' capacity in supplying pollination was low, fragmentation decreased pollination. When this capacity was very high, landscapes with a high degree of fragmentation showed higher levels of pollination. There was an exception for habitat amounts less than 0.1 of the entire landscape that increasing edge density, aggregation, and the number of patches, resulted in increasing pollination in all scenarios.

Using the Lonsdorf model for estimating habitat loss and fragmentation effects on pollination service

One of the most important issues related to landscape ecology and ecosystem services is finding the pattern of habitat patches that offers the highest pollination in agricultural landscapes. In this regard, two processes of habitat loss and fragmentation strongly affect the relationship between pollination and the pattern of habitat patches. In the present study, we aimed to examine the effects of habitat loss and fragmentation on pollination separately. For this purpose, first, we generated different simulated agricultural landscapes, including two habitats of forest and agriculture. Then, according to the Lonsdorf model, we estimated the potential of the simulated landscapes in providing pollination in different scenarios. Finally, using statistical models, we estimated the effects of habitat loss and fragmentation on pollination at the landscape and farm levels. Our results showed that the effects of habitat loss and fragmentation on pollination were completely different at the landscape and farm levels. At the landscape level, fragmentation negatively affected pollination, but at the farm level, the maximum pollination rate was observed in the landscapes with a high degree of fragmentation. Regarding the habitat loss effects, our results showed that pollination decreased linearly at the landscape level as habitat amount decreased, but at the farm level, it decreased exponentially. The present study considered the level of analysis (i.e., landscape and farm levels) as a critical factor affecting pollination changes caused by fragmentation. We showed that using the Lonsdorf model could lead to confusing results for the landscape ecologists and alert farmers who want to reduce the adverse effects of fragmentation on their products by creating new forest patches. Therefore, agriculturalists and landscape ecologists should consider that the pollination rate at the landscape and farm levels is completely different according to the model and provide contradictory results about the process of habitat loss effects on pollination.