Appreciating Ecological Complexity: Habitat Contours as a Conceptual Landscape Model

Abstract:  Organisms respond to their surroundings at multiple spatial scales, and different organisms respond differently to the same environment. Existing landscape models, such as the "fragmentation model" (or patch-matrix-corridor model) and the "variegation model," can be limited in their ability to explain complex patterns for different species and across multiple scales. An alternative approach is to conceptualize landscapes as overlaid species-specific habitat contour maps. Key characteristics of this approach are that different species may respond differently to the same environmental conditions and at different spatial scales. Although similar approaches are being used in ecological modeling, there is much room for habitat contours as a useful conceptual tool. By providing an alternative view of landscapes, a contour model may stimulate more field investigations stratified on the basis of ecological variables other than human-defined patches and patch boundaries. A conceptual model of habitat contours may also help to communicate ecological complexity to land managers. Finally, by incorporating additional ecological complexity, a conceptual model based on habitat contours may help to bridge the perceived gap between pattern and process in landscape ecology. Habitat contours do not preclude the use of existing landscape models and should be seen as a complementary approach most suited to heterogeneous human-modified landscapes.     

Rethinking the Effectiveness of Public Protected Areas in Southwestern China

Abstract:  It is internationally recognized that conservation policies should respect indigenous cultures and consider the livelihoods of people affected by conservation restrictions. Countering this are concerns that human occupation and use of natural reserves is incompatible with conservation aims. But in China today the continued use and management of natural areas by local communities is likely to deliver better conservation outcomes than the current drive to establish public protected areas. The effectiveness of many protected areas in China is compromised by institutional conflicts, lack of ongoing financial and technical support, confusion between the objectives of generating revenue and conservation, dubious scientific definitions, lack of community trust in policies, and obscure user rights and land tenures. Southwestern China—one of the most biologically and ethnologically diverse areas on Earth—is a good illustration of a place where culture and biological diversity are closely linked. The indigenous people in this area have shown that local livelihood practices can be advantageous for the long-term maintenance of conservation goals. Rather than creating new protected areas, we argue that China is better advised to support ongoing sustainable use of natural areas by the people who have lived and nurtured these environments for generations .     

Body Size Variation of Mammals in a Fragmented, Temperate Rainforest

Abstract:  Body size is perhaps the most important trait of an organism, affecting all of its physiological and ecological processes and, therefore, fundamentally influencing its ability to survive and reproduce in different environments, including those that have been modified by human activities. We tested the hypothesis that anthropogenic transformation of old-growth forest landscapes can result in significant intraspecific changes in body size of resident biotas. We collected data on five species of nonvolant mammals (common deer mouse [Peromyscus maniculatus ], northwestern deer mouse [P. keeni] , southern red-backed vole [Clethrionomys gapperi ], montane shrew [Sorex monticolus] , and Trowbridge's shrew [S. trowbridgii] ) to test whether body size (mass and length) of these species varied across types of land cover (macrohabitats) and along elevational gradients of the fragmented, temperate rainforest of Olympic National Forest (Washington, U.S.A.). We measured 2168 and 1134 individuals for body mass and body length, respectively. Three species ( P. keeni , S. monticolus , and S. trowbridgii ) exhibited significantly different body size among macrohabitats: individuals from fragments were smaller than those in old-growth corridors and those in more extensive stands of old-growth forest. Body size of P. keeni was significantly correlated with elevation along corridors, peaking near the medial reaches of the corridors. The effects of anthropogenic transformations of this landscape of old-growth, temperate rainforest, although not universal among the five species, were significant and rapid—developing in just a few decades following tree harvests. Thus, anthropogenic fragmentation may influence not only the diversity, species composition, and densities of local biotas, but also one of the most fundamental and defining characteristics of native species—their body size.     

Predicting Human-Carnivore Conflict: a Spatial Model Derived from 25 Years of Data on Wolf Predation on Livestock

Abstract:  Many carnivore populations escaped extinction during the twentieth century as a result of legal protections, habitat restoration, and changes in public attitudes. However, encounters between carnivores, livestock, and humans are increasing in some areas, raising concerns about the costs of carnivore conservation. We present a method to predict sites of human-carnivore conflicts regionally, using as an example the mixed forest-agriculture landscapes of Wisconsin and Minnesota (U.S.A.). We used a matched-pair analysis of 17 landscape variables in a geographic information system to discriminate affected areas from unaffected areas at two spatial scales (townships and farms). Wolves ( Canis lupus ) selectively preyed on livestock in townships with high proportions of pasture and high densities of deer ( Odocoileus virginianus ) combined with low proportions of crop lands, coniferous forest, herbaceous wetlands, and open water. These variables plus road density and farm size also appeared to predict risk for individual farms when we considered Minnesota alone. In Wisconsin only, farm size, crop lands, and road density were associated with the risk of wolf attack on livestock. At the level of townships, we generated two state-wide maps to predict the extent and location of future predation on livestock. Our approach can be applied wherever spatial data are available on sites of conflict between wildlife and humans.     

Effects of Roads on the Structure of Freshwater Turtle Populations

Abstract:  Road mortality has the potential to alter the structure of turtle populations because turtle populations are highly sensitive to additive sources of adult mortality. To address the issue, we captured painted turtles (   Chrysemys picta ; n = 174) and snapping turtles (   Chelydra serpentina ; n = 56) in 18 wetlands surrounded by low road density (≤1.5 km roads/km² of landscape) and 17 wetlands surrounded by high road density (>1.5 km/km²) in central New York in 2002. High road density was associated with male-biased sex ratios in painted turtles (74% vs. 54% males; p = 0.01) and snapping turtles (95% vs. 74% males; p = 0.08), whereas turtle morphology and abundance were not associated with road density. Disproportionate road mortality of females on nesting migrations is the most likely cause of skewed sex ratios.     

Reconciling Salvage Logging of Boreal Forests with a Natural-Disturbance Management Model

Abstract:  In North American boreal forests, wildfire is the dominant agent of natural disturbance. A natural-disturbance model has therefore been promoted as an ecologically based approach to forest harvesting in these systems. Given accelerating resource demands, fire competes with harvest for timber, and there is increasing pressure to salvage naturally burned areas. This creates a management paradox: simultaneous promotion of natural disturbance as a guide to sustainability while salvaging forests that have been naturally disturbed. The major drivers of postfire salvage in Canadian boreal forests are societal perceptions, overallocation of forest resources, and economic and policy incentives, and postfire salvage compromises forest sustainability by diminishing the role of fire as a critical, natural process. These factors might be reconciled through consideration of fire in resource allocations and application of active adaptive management. We provide novel treatment of the role of burn severity in mediating biotic response by examining its influence on the amount, type, and distribution of live, postfire residual material, and we highlight the role of fire in shaping spatial and temporal patterns in forest biodiversity. Maintenance of natural postfire forests is a critical component of an ecosystem-based approach to forest management in boreal systems. Nevertheless, present practices focus heavily on expediting removal of timber from burned forests, despite increasing evidence that postfire communities differ markedly from postharvest systems, and there is a mismatch between emerging management models and past management practices. Policies that recognize the critical role of fire in these systems and facilitate enhanced understanding of natural system dynamics in support of development of sustainable management practices are urgently needed.     

Designing a Conservation Landscape for Tigers in Human-Dominated Environments

Abstract:  Wildlife populations in small, isolated reserves face genetic and demographic threats to their survival. To increase the probability of long-term persistence, biologists promote metapopulation management, in which breeding subpopulations are protected as source pools. Animals that disperse from the source pools increase the probability of persistence of the metapopulation across the greater landscape. We used a geographic information system (GIS)–based, cost-distance model to design a conservation landscape along the Himalayan foothills for managing a metapopulation of Asia's largest predator, the tiger ( Panthera tigris ). The model is based on data from 30 years of field research on tigers, recent satellite imagery, and a decade of buffer-zone restoration in this region. We used the model to (1) identify potential dispersal corridors for tigers; (2) identify strategic transit refuges; and (3) make recommendations for off-reserve land management and restoration to enhance the potential of corridors for tigers. This tool can aid the design of conservation landscapes for other endangered, wide-ranging species in human-dominated environments.