Prospects for biodiversity conservation in the Atlantic Forest: Lessons from aging human-modified landscapes

Recent global assessments have shown the limited coverage of protected areas across tropical biotas, fuelling a growing interest in the potential conservation services provided by anthropogenic landscapes. Here we examine the geographic distribution of biological diversity in the Atlantic Forest of South America, synthesize the most conspicuous forest biodiversity responses to human disturbances, propose further conservation initiatives for this biota, and offer a range of general insights into the prospects of forest species persistence in human-modified tropical forest landscapes worldwide. At the biome scale, the most extensive pre-Columbian habitats across the Atlantic Forest ranged across elevations below 800 masl, which still concentrate most areas within the major centers of species endemism. Unfortunately, up to 88% of the original forest habitat has been lost, mainly across these low to intermediate elevations, whereas protected areas are clearly skewed towards high elevations above 1200 masl. At the landscape scale, most remaining Atlantic Forest cover is embedded within dynamic agro-mosaics including elements such as small forest fragments, early-to-late secondary forest patches and exotic tree monocultures. In this sort of aging or long-term modified landscapes, habitat fragmentation appears to effectively drive edge-dominated portions of forest fragments towards an early-successional system, greatly limiting the long-term persistence of forest-obligate and forest-dependent species. However, the extent to which forest habitats approach early-successional systems, thereby threatening the bulk of the Atlantic Forest biodiversity, depends on both past and present landscape configuration. Many elements of human-modified landscapes (e.g. patches of early-secondary forests and tree monocultures) may offer excellent conservation opportunities, but they cannot replace the conservation value of protected areas and hitherto unprotected large patches of old-growth forests. Finally, the biodiversity conservation services provided by anthropogenic landscapes across Atlantic Forest and other tropical forest regions can be significantly augmented by coupling biodiversity corridor initiatives with biota-scale attempts to plug existing gaps in the representativeness of protected areas.     

Interactions between protected areas and their surroundings in human-dominated tropical landscapes

Protected areas (PAs) often depend on landscapes surrounding them to maintain flows of organisms, water, nutrients, and energy. Park managers have little authority over the surrounding landscape although land use change and infrastructure development can have major impacts on the integrity of a PA. The need for scientifically-based regional-scale land use planning around protected areas is acute in human-dominated landscapes to balance conservation goals with livelihood needs for fuelwood, fodder, and other ecosystem services. As a first step, we propose the designation of a “zone of interaction” (ZOI) around PAs that encompasses hydrologic, ecological, and socioeconomic interactions between a PA and the surrounding landscape. We illustrate the concept by delineating the ZOI in three Indian PAs - Kanha, Ranthambore, and Nagarahole - using remote sensing, population census, and field data. The ZOI in Ranthambore is three times the size of the park and is largely defined by the socioeconomic interactions with surrounding villages. Ranthambore is located in headwaters and wildlife corridors are largely severed. In Nagarahole, the ZOI is more than seven times larger than the park and includes upstream watershed and elephant corridors. Kanha’s ZOI is approximately four times larger than the park and is mostly defined by contiguous surrounding forest. The three examples highlight the differing extents of ZOIs when applying equivalent criteria, even though all are located in densely-populated landscapes. Quantitative understanding of which activities (e.g. collection of forest products, grazing, road construction, tourism development) and which locations within the ZOI are most crucial to conservation goals will enable improved land use planning around PAs in human-dominated landscapes.     

Gaps in the protected area network for threatened Afrotropical birds

Protected areas established for wildlife conservation (IUCN category I-VI protected areas) or for forest and watershed conservation (forest reserves) across mainland sub-Saharan Africa have high biodiversity values. However, they fail to cover over half of the 106 threatened bird species, and thus leave these vulnerable to extinction. An analysis of Red List bird species that are not represented in existing reserves indicates gaps in the current network of protected areas, namely: Mt. Cameroon-Bamenda highlands (Cameroon), the Angolan scarp (Angola), the Drakensberg Highlands (South Africa), the Highveld (South Africa), the Eastern Arc Mountains (Tanzania), the eastern African coastal forest mosaic (Kenya and Tanzania), the Albertine Rift (Uganda, Rwanda, Burundi, eastern Democratic Republic of Congo and western Tanzania), and the Ethiopian Highlands. The addition of Forest Reserves to the existing protected areas closes some of the reservation gaps for threatened birds in Africa. We suggest that these Forest Reserves should be included within official lists of protected areas, and that National forestry authorities be encouraged to manage these areas. Publication of scientific articles showing the conservation value of Forest Reserves is needed to raise local and international support and funding.     

Village size and forest disturbance in Bhadra Wildlife Sanctuary, Western Ghats, India

Habitat fragmentation, land cover change and biodiversity loss are often associated with village communities in protected areas, but the extent and intensity of such impacts are often inadequately assessed. We record resource use and depletion by human inhabitants by conducting ecological surveys in six villages and social surveys in all 13 villages of varying sizes in India’s Bhadra Wildlife Sanctuary (492 km²). We examined the occurrence of 10 regionally-specific ecological indicators that encompassed several aspects of human activities. Thirty transects with 180 total sampling locations recorded the occurrence of these specific habitat disturbance variables. High correlations between the variables led to the use of principal component analysis to derive an effective summary index that reflected disturbance intensity and determined village ecological impacts spatially. A generalized linear model was fit to determine the rate at which disturbance decreases as we move away from village centers. Our model indicates that village size class, distance from the village and proximity to other villages were significant predictors of the disturbance index. The index distinguished each village’s spatially explicit ecological impact. We estimated that an average area of 23.7 km² of the forest surrounding the six focal villages was altered by human activities. These six villages have directly impacted 8-10% of this protected area.     

Patterns and correlates of human–elephant conflict around a south Indian reserve

Success stories in Indian conservation also carry opportunity costs in the form of human–wildlife conflicts, especially to people living in close proximity with wildlife. In India, human–wildlife conflict is a serious challenge to wildlife conservation, which needs a much-improved scientific and social understanding. In this study, I assess the patterns and correlates of human–elephant conflicts around Nagarahole National Park, southern India. I hypothesised that human and livestock demographic variables, and factors such as cropping patterns, availability of irrigated land around the national park, and protected area frontage to be the underlying correlates of conflict. Using applications and documents filed with the wildlife department by affected farmers during the period 2006–2009, I analysed crops affected, compensation payments made by the Government, spatio-temporal patterns of conflict and identified the key correlates of human–elephant conflict. 98.8% of the conflict incidences occurred in villages that lie within 6 km from the national park boundary. Of the 26 crop types affected by elephants, finger millet, maize, cotton, paddy and sugarcane formed 86.34% of the total crop losses. Conflict frequencies were highest during August–November, a period when there was a decrease in rainfall and important crops such as finger millet, maize and paddy were ripening. Multiple linear regression results suggest that villages with higher protected area frontage and unirrigated land were key variables underlying conflict frequency. However, results from this study suggests that there are other probable factors such as elephant behaviour, movement patterns and/or maintenance of physical barriers which could be more important determinants of conflict.     

Landscape patterns influencing bird assemblages in a fragmented neotropical cloud forest

The cloud forest is one of the rarest and most threatened ecosystems in Mexico, although it contributes highly to the country's biological diversity and provides important ecological services. It is a naturally fragmented ecosystem, but anthropogenic deforestation and fragmentation has been severe. Consequently, it is essential to identify landscape patterns critical for the conservation of cloud forest. In order to understand how landscape patterns affect diversity in this ecosystem, this study explores the consequences of cloud forest fragmentation on bird diversity in eastern Mexico. I analysed the response of bird species richness and abundance as a function of forest fragment size, shape, topographical complexity, altitudinal range, connectivity, and proportion of landscape forested area in a system of 13 cloud forest fragments. Fragment shape was the main characteristic positively related to species richness in the bird community, but a differential response to landscape patterns was also detected. Fragment size was the main characteristic influencing the segment of the bird community depending mostly on forest, that is to say, forest interior and generalist species. In contrast, the extent of forest edge, expressed as fragment shape, produced a positive response of forest border species. Both, forest dependent and border dependent species positively responded to the extent of their suitable habitat. The immediate and most effective ecologically oriented conservation strategy for the region is the conservation of the largest cloud forest fragments.     

Effects of agricultural landscape and pesticides on parasitism in native bullfrogs

Native amphibian populations are shrinking worldwide, and both parasitic infections and environmental stress from agriculture have been implicated. We investigated the principal hypothesis that environmental by-products of agricultural activity mediate parasitism in native frogs. Bullfrogs were collected from wetlands with variable landscape disturbance and water quality and examined for helminth parasites. We predicted that pesticide pollution and landscape development would be significant factors shaping the parasite communities and populations. Parasite diversity and species richness were lower in wetlands impacted by both pesticides and land use. Two parasite groups, direct life-cycle nematodes and echinostomes, were common in polluted habitats, potentially increasing frog pathology and mortality risk. In areas with agricultural landscape and reduced forest cover, parasite diversity and species richness were low, perhaps because of less parasite transmission from birds and mammals. This result suggests that land development limits terrestrial vertebrate access to wetlands. Our results indicate that parasite abundance and community structure in wetlands are influenced by factors operating locally within the wetland and more broadly in the surrounding landscape. We suggest that parasite communities in amphibians are effective indicators of ecosystem health and animal biodiversity, and thus useful tools for conservation biology.     

The efficacy of small-scale conservation efforts, as assessed on Australian golf courses

Habitat remnants on urban green-space areas (i.e. parks, gardens and golf courses) sometimes provide refuge to urban-avoiding wildlife, leading some to suggest these areas may play a role in wildlife conservation if they are appropriately designed and managed. The high densities observed on some green-space areas may however be attributed to external influences. Localised efforts to enhance the habitat value of urban green-space areas may therefore have little more than a cosmetic effect. This study investigated environmental factors influencing bird, reptile, mammal and amphibian diversity on Australian golf courses to assess the efficacy of small-scale conservation efforts. Abundance and species richness did not simply reflect local habitat qualities but were instead, partly determined by the nature of the surrounding landscape (i.e. the area of adjacent built land, native vegetation and the number of connecting streams). Vertebrate abundance and species richness were however, also associated with on-site habitat characteristics, increasing with the area of native vegetation (all vertebrates), foliage height diversity and native grass cover (birds), tree density, native grass cover and the number of hollows (mammals), woody debris, patch width and canopy cover (reptiles), waterbody heterogeneity and aquatic vegetation complexity (frogs). Localised conservation efforts on small land types can benefit urban-avoiding wildlife. Urban green-space areas can provide refuge to urban-avoiding vertebrates provided combined efforts are made at patch (management), local (design) and landscape (planning) scales.     

Identification of de facto protected areas in boreal Canada

Canada is dominated by remote wilderness areas that make important conservation contributions, but are currently only protected de facto by their inaccessibility. Mechanisms for the identification and formal protection of such areas can help ensure that they continue to function naturally and provide essential ecosystem services. However, a lack of spatially explicit, publicly available sources of data on anthropogenic disturbances and natural resource extraction challenges the development of detailed wilderness inventories. We suggest that landscape structure can be used to classify areas of natural landscapes, as trained by the landscape structure of protected areas, and demonstrate this approach by mapping de facto protected areas in Canada’s boreal forest. Overall, between 50%, based on landscape structure, and 80%, based on anthropogenic infrastructure alone, of Canada’s boreal zone exists in large, intact blocks. The true extent of boreal wilderness likely falls within this range, as existing infrastructure datasets may omit disturbance and the protected area network in far northern areas proved inadequate to train effective wilderness classifications. We anticipate that such efforts may be improved by refining the identification of training areas or by classifying along additional landscape metrics. Nevertheless, the areas identified are valuable candidates for protected area expansion, and can contribute to a reserve network that meets national and regional conservation targets and is representative of the range of vegetation productivities, which was used as a biodiversity surrogate. Our general approach need not be limited to the boreal forest, as it has the potential to successfully identify relatively undisturbed (or less disturbed) areas over a range of systems and across levels of human influence.     

Sustaining biodiversity conservation in human-modified landscapes in the Western Ghats: Remnant forests matter

Human-modified tropical landscapes under semi-natural or agro-ecosystems often harbor biodiversity of significant conservation value. In the Western Ghats of India, these ecosystems also provide connectivity between protected areas and other remnant forests. We investigated the conservation value of these landscapes and agro-ecosystems using results from 35 studies covering 14 taxonomic groups. Large, conspicuous taxonomic groups and tree-covered land-use types have received much focus in this area of research in the Western Ghats. We computed a response ratio defined as the log ratio of species richness in human land use to species richness in forest control site from 17 studies. In a meta-analysis, we investigated variation of this ratio across studies with respect to three variables: taxonomic group, the land-use type sampled and the extent of forest cover within the study landscape. Higher forest cover within the landscape emerged as a major positive influence on biodiversity in human-modified landscapes for vertebrates and vegetation while no patterns emerged for invertebrates. Our results suggest that loss of remnant forest patches from these landscapes is likely to reduce biodiversity within agro-ecosystems and exacerbate overall biodiversity loss across the Western Ghats. Conservation of these remnant forest patches through protection and restoration of habitat and connectivity to larger forest patches needs to be prioritized. In the densely populated Western Ghats, this can only be achieved by building partnerships with local land owners and stakeholders through innovative land-use policy and incentive schemes for conservation.     

Discriminating between village and commercial hunting of apes

Hunting is the major driver of large mammal decline in Central African forests. In slowly reproducing species even low hunting pressure leaves spatial gradients with wildlife density increasing with distance from transport routes and human settlements. Park management can use this pattern formation to identify sources of threats, but also to discriminate between different threat scenarios, such as the impact of subsistence vs. commercial hunting. We conducted an ape survey in the mountainous Moukalaba Doudou National Park, Gabon, to evaluate whether potential population gradients would emanate from the three human population centers in the region or the villages surrounding the park. Using generalized linear modeling we found hill slope as a good predictor of ape nest occurrence probability and the distance to human population centers a better predictor of ape nest density and ape nest group size than distance to villages. In fact ape nest density was three times lower at the park borders close to the human population centers than in the park’s interior. The results indicate that Moukalaba’s ape population is more impacted by commercial than subsistence hunting and suggest that park management should focus conservation efforts on the human population centers. We conclude that in particular for slowly reproducing species geographic information on wildlife population gradients are of additional value for guiding protected area management. The hunting impact on those species might be easily underestimated, if derived only from market surveys or transport route controls, where they are only rarely found.     

Comparing bird community responses to forest fragmentation in two lowland Central American reserves

Habitat loss and fragmentation reduce diversity of tropical bird communities, but the predictability of how communities in fragments disintegrate over time remains unclear. We compared bird community changes of two lowland forest reserves, La Selva Biological Station (LSBS), Costa Rica and Barro Colorado Island (BCI), Panama, both approximately the same size (1500 ha) and at similar latitude (9-10 N) in Central America. Both reserves are losing bird species despite LSBS’s connection to an existing large park (incomplete isolation) and BCI’s favorable location within a largely forested landscape. We examined characteristics of guilds and species lost from the sites to determine whether patterns were similar, and thus predictable. Some of the same guilds declined at both reserves, particularly insectivores and ground/understory nesters. At LSBS mixed-species flock participants, forest species, and burrow-nesters also declined or became extirpated disproportionately. At BCI edge species became extirpated. Body mass was a poor predictor of species and guild loss at both sites, except for carnivores at La Selva. Thus, fragmentation appears to influence some guilds more than others, but which species decline or disappear in tropical forest fragments is also influenced by site-specific factors, mostly yet to be determined. We need to understand such idiosyncratic effects of fragmentation better, rather than rely on one-size-fits-all management plans to conserve bird communities in tropical forest fragments.     

Evaluating hedgerow corridors for the conservation of native forest herb diversity

The maintenance of connecting habitats such as hedgerows in production landscapes could become increasingly critical as species migration is expected to accelerate with climate change. Species of particular conservation interest that could benefit from connecting habitats especially in agroecosystems are native forest herbs. It is still unclear, however, which hedgerow habitats have the best potential of supporting diverse forest herb communities, making it hard to target particular structures for conservation. Our objective was to identify the local and landscape characteristics of hedgerows that could help predict their potential at maximizing the richness, abundance, and diversity of native forest herbs of temperate deciduous forests of North-East America. We used multiple regression, Moran’I correlograms, and conditional autoregressive models to assess the effect of landscape and historical variables (hedgerow age, amount of adjacent forest cover, connection to forests and other hedgerows) and of local variables (hedgerow width, canopy cover, cover of other species) on the response variables. The results show an increase in forest herb diversity and abundance in hedgerows with time and with increasing nearby forest cover. Local factors such as greater width and reduced cover of other species also relate to a greater abundance and diversity of forest herbs in linear habitats. The fact that forest herb communities can reassemble in hedgerow corridors with time implies that there could be long-term benefits in maintaining and even creating linear habitats where there is a pool of dispersing forest herbs.     

Dissecting habitat loss and fragmentation effects following logging in boreal forest: Conservation perspectives from landscape simulations

Habitat loss and fragmentation are recognized as major threats to biodiversity. Their respective effects, however, are sometimes not well distinguished, even though habitat loss is recognized as the most important source of variation affecting species abundance and richness at the landscape scale. As ‘habitat’ is a species-specific concept (based on species perception of its environment), habitat loss and fragmentation studies should be conducted on a species-specific basis. We here assessed the influence of habitat loss and fragmentation in the context of a boreal forest considering forest clearcutting as an anthropogenic disturbance inducing mature forest loss and fragmentation that has a potential impact on wildlife. Using 16 simulated patterns of mature forest loss and fragmentation and three natural landscapes as replicates, we assessed the respective influence of forest loss and fragmentation on the abundance of 10 bird species common in the boreal forest of eastern Canada. Species–habitat relationships were modeled through habitat use models that were utilized to predict abundance of the 10 species within each combination of loss and fragmentation patterns (3 landscapes × 16 patterns). We used three-way ANOVAs to assess the effects of mature forest loss, fragmentation and replicates (random effect) on species abundance. Our results indicated that: (1) variation in species abundance mostly depended on mature forest loss, followed by static landscape attributes other than cutovers (e.g. streams, lakes, roads) and finally by fragmentation and (2) responses to mature forest loss and fragmentation differed among species, not necessary in relation to the successional status but in relation to their perception of their environment. Decreasing detrimental effects of mature forest loss through conservation of large continuous patches of forest may be suitable to maintain abundances of mature forest bird species. Our results highlight that studies aiming to quantify effects of habitat loss and fragmentation on wildlife should be conducted on a species-specific basis and use several landscape replicates to avoid potentially biased results.     

Realities of documenting wildlife corridors in tropical countries

Connectivity is regarded as vital in conservation planning but the whereabouts of remaining wildlife corridors and dispersal areas in most tropical countries are poorly documented. With local experts, we compiled an annotated list of the most important wildlife corridors remaining on mainland Tanzania, information on the status of each corridor, wildlife using these corridors, and threats to them. We discovered that the concept of a wildlife corridor differs greatly between different people working in the same country, so we divided these into five working categories. The most common categories were those identified by known movements of animals between two protected areas, or simply proposed connections between important habitats. In Tanzania, the majority of documented corridors now seem to be in a critical condition, that is, they may have less than 5 years remaining before they disappear, judging by current rates of land use change. Five corridors are in extreme condition and could disappear within 2 years unless immediate action is taken. These pressing problems – and our experience in Tanzania – indicate that surveys of remaining wildlife corridors may need urgent documentation in other countries too and that collators should maintain loose definitions of corridors, accept data of variable quality and give information to authorities as soon as possible in order to maximize the chances of saving these conservation assets.     

Thresholds in the long-term responses of breeding birds to forest cover and fragmentation

Mitigating the effects of habitat loss requires estimating the minimum amount of habitat necessary for the persistence of wildlife populations in a changing landscape. Assessing minimum habitat amounts, however, relies on identifying ecological thresholds in species’ responses to landscape change. Using two repeated state-wide atlases, our objective was to investigate the responses of 25 forest birds to a range of forest cover and fragmentation. Repeat atlases allow for the analysis of four population dynamics including: (1) colonization, (2) persistence, (3) extinction, and (4) absence. Our objective was to test the hypothesis that forest birds demonstrated thresholds in these four basic dynamics to varying amounts of forest cover and fragmentation.We found thresholds to be a common, though not pervasive, characteristic of how forest birds respond to forest cover and pattern. We found that the probability of persistence was positively correlated with forest cover and 22 species demonstrated threshold responses. In addition, 15 of 25 birds demonstrated discrete thresholds in extinction dynamics. The existence of a colonization threshold has received significantly less attention in ecology. We also found that 17 out of 25 species demonstrated thresholds in their colonization response to a greater amount of forest cover. The effects of forest fragmentation, independent of forest amount, were less clear. We found support for incorporating the effects of fragmentation, but this fragmentation effect was found both below and above threshold points. We conclude that incorporating ecological thresholds in environmental planning should be species-specific and focus on populations on the verge of rapid ecological change.     

Effects of landscape characteristics on amphibian distribution in a forest-dominated landscape

We investigated the influence of landscape and wetland characteristics on pond-breeding amphibian assemblages in south-central New Hampshire, a relatively low populated and heavily forested region of the northeastern United States. This allowed us to better understand landscape influences in less disturbed areas, and to determine critical landscape disturbance thresholds, above which amphibians are negatively impacted. We sampled 61 wetlands for larval amphibians in 1998 and 1999 to examine the influence of forest cover and road density (at seven buffer distances between 100 and 2000 m) and wetland characteristics on larval amphibian assemblages. Assemblages were influenced primarily by forest cover and wetland hydroperiod. Species richness was most strongly influenced by the proportion of forest cover within 1000 m of the wetland. Several species were also influenced by forest cover, but were differentially influenced by buffer widths. Our study suggests that, at least in the northeast US, wetlands with <40% forest cover within a 1000 m radius may have depauperate larval amphibian assemblages, and forest cover above 60% within a 1000 m radius is likely to ensure species rich and abundant larval amphibian assemblages. Given the above, current federal and state regulations that focus amphibian protection efforts on narrow terrestrial buffers surrounding wetlands are likely to be inadequate.     

Why do local households harvest forest products? A case study from the southern Western Ghats, India

Deforestation in tropical countries has been partly attributed to the non-sustainable harvesting of forest biomass by local communities. We conducted a survey among 786 households in 31 agricultural villages adjoining the eastern boundary of the Kalakad-Mundanthurai Tiger Reserve, in the southern Western Ghats to see whether household wealth, social status, literacy and distance to the forest boundary influenced resource harvesting. Fuel-wood, fodder and green leaves were the major products harvested in this agricultural region. The effect of distance from the reserve boundary differed with the product harvested and its use value. Distance was a constraint for households that harvested for domestic consumption, whereas it was not significant for households that harvested for earnings. Wealth was independent of resource interest in the forest, except for the poorer lower caste households with lower levels of literacy that sold fuel-wood to earn a living. Wealthier households harvested green leaves for fertilizing their fields, and fodder harvest was related to livestock ownership. The lower cost of forest products compared to commercially available substitutes probably fuelled extraction. Forest products contributed disproportionately to household consumption as compared with household earnings. Discouraging the harvest of forest products within protected areas might be the only viable conservation strategy.     

Community, lions, livestock and money: A spatial and social analysis of attitudes to wildlife and the conservation value of tourism in a human–carnivore conflict in Botswana

We quantified livestock (cattle, shoats, horses and donkeys) losses to lions (Panthera leo) and attitudes to lions, livestock losses and tourism among livestock owners, village residents and tourism workers around Makgadikgadi Pans National Park in Botswana. Losses were not correlated with the size or structure of livestock enclosures, numbers of dogs or herders. Rather losses increased with the amount of livestock owned. Most were stray animals preyed upon at night. Attitudes to wildlife, conservation and lions were also not consistently distributed within the society we studied. Negative attitudes to lions were almost ubiquitous among cattleposts but less widespread among people living in the more urbanized society of villages or among people working in tourism.Although four tourist camps were operating in the area, benefits from these operations were largely limited to employees. Despite considerable sums of money being paid to Botswana by local tourist facilities few respondents viewed tourism as valuable and most felt that the government and not they or their community was the main beneficiary of tourism. Tourism employees made up a small sub-section of the adult population drawn predominately from larger villages while the costs of livestock losses were spread among cattleposts near the park boundary. These same cattlepost respondents were not prepared to improve stock care to protect livestock, but indicated a willingness to kill lions instead. If tourism is to play a role in reducing human–wildlife conflict, communities must not be regarded as homogenous entities into which to distribute benefits evenly. Benefits might usefully be distributed in relation to the costs of coexisting with wildlife or used as incentives to better protect livestock or other human resources.     

庆阳市土地利用变化的景观生态效应研究

本文以甘肃省庆阳市为研究对象,选取2005年和2010年Landsat TM影像作为基本信息源,借助GIS技术和Fragstas 4.0软件,研究庆阳市的土地利用/覆被变化及其景观生态效应。结果表明:（1）研究时段内土地利用/覆盖变化较大,各土地类型间转换频繁。落叶阔叶林面积大幅度减少,减少的落叶阔叶林转变为灌木林,且落叶阔叶林减少量大于灌木林增加量。耕地面积逐渐减少,草地、居住地和交通用地明显增加。（2）庆阳市斑块数目较多,平均斑块面积在增加,但景观丰富度、边缘密度和斑块密度呈减小趋势。斑块破碎化程度在减小,景观空间异质性减小和均质化发展使得景观稳定性降低。林草地边缘效应的降低,使其景观生态功能减弱。