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Las zonas rurales están expuestas a procesos de fragmentación de bosques debido al desarrollo de actividades agropecuarias ambientalmente no sostenibles. Ante esta situación, surge el interés de estudiar la fragmentación y conectividad del bosque en una subcuenca agropecuaria en el noroeste del Valle Central de Costa Rica. Se propone, mediante el uso de aplicaciones SIG, una red de conectividad basada en enlaces de vegetación a partir de la red de drenaje. Se encontró que la fragmentación en la subcuenca es diferencial, en virtud de la distribución e intensidad de los usos de la tierra. Así, las partes altas presentan mayor cobertura y continuidad del bosque, mientras que en las zonas bajas la vegetación remanente se localiza casi exclusivamente en los márgenes de los ríos. Los usos que generan mayor fragmentación son principalmente los cultivos hortícolas, seguidos de los pastos, pastos con árboles dispersos y, en menor grado, los usos urbanos localizados generalmente a lo largo de las vías de comunicación.Ideas destacadas: artículo de investigación donde se analiza la fragmentación y conectividad del bosque en una subcuenca agropecuaria, mediante aplicaciones sig, para la propuesta de enlaces de vegetación con la red de drenaje como eje principal.

Loss of natural forests by forest clearcutting has been identified as a critical conservation challenge worldwide. This study addressed forest fragmentation and loss in the context of the establishment of a functional green infrastructure as a spatiotemporally connected landscape-scale network of habitats enhancing biodiversity, favorable conservation status, and ecosystem services. Through retrospective analysis of satellite images, we assessed a 50- to 60-year spatiotemporal clearcutting impact trajectory on natural and near-natural boreal forests across a sizable and representative region from the Gulf of Bothnia to the Scandinavian Mountain Range in northern Fennoscandia. This period broadly covers the whole forest clearcutting period; thus, our approach and results can be applied to comprehensive impact assessment of industrial forest management. The entire study region covers close to 46,000 km² of forest-dominated landscape in a late phase of transition from a natural or near-natural to a land-use modified state. We found a substantial loss of intact forest, in particular of large, contiguous areas, a spatial polarization of remaining forest on regional scale where the inland has been more severely affected than the mountain and coastal zones, and a pronounced impact on interior forest core areas. Salient results were a decrease in area of the largest intact forest patch from 225,853 to 68,714 ha in the mountain zone and from 257,715 to 38,668 ha in the foothills zone, a decrease from 75% to 38% intact forest in the inland zones, a decrease in largest patch core area (assessed by considering 100-m patch edge disturbance) from 6114 to 351 ha in the coastal zone, and a geographic imbalance in protected forest with an evident predominance in the mountain zone. These results demonstrate profound disturbance of configuration of the natural forest landscape and disrupted connectivity, which challenges the establishment of functional green infrastructure. Our approach supports the identification of forests for expanded protection and conservation-oriented forest landscape restoration. La pérdida de bosques naturales por causa de la tala uniforme de árboles en los mismos ha sido identificada como unreto muyimportantepara la conservación global. Esteestudioabordó la fragmentación y pérdida de bosques en el contexto del establecimiento de una infraestructura verde funcional como una red de hábitats a escala de paisaje conectados espacio-temporalmente que mejoren la biodiversidad, los estados favorables de conservación y los servicios ambientales. Por medio de un análisis retrospectivo de imágenes satelitales evaluamos una trayectoria de impacto espacio-temporal de 50 a 60 años de tala uniforme sobre bosques boreales naturales y casi naturales en una región considerable y representativa desde el Golfo de Botnia hasta la Cordillera Escandinava en el norte de Fenoescandia. Este rango cubre todo el periodo de tala uniforme en el bosque en términos generales; por lo tanto, nuestra metodología y resultados pueden aplicarse a la evaluación completa del impacto del manejo industrial de bosques. Toda la región de estudio cubría hasta 46,000 km² de paisaje dominado por bosque en una etapa tardía de la transición entre el estado natural o casi natural y el estado de uso de suelo modificado. Encontramos una pérdida sustancial de bosque intacto, particularmente para áreas grandes y contiguas, una polarización espacial del bosque restantea una escala regional en la que tierra adentro hay mayores afectaciones que en las zonas montañosas y costeras, y un impacto pronunciado sobre las áreas nucleares de los bosques interiores. Los resultados salientes fueron una disminución en el área del fragmento más grande de bosque intacto de 225, 853 a 68, 714 ha en la zona montañosa y de 257, 715 a 38, 668 ha en la zona de pie de monte, una disminución del 75% al 38% de bosque intacto en las zonas tierra adentro, una disminución en el área nuclear del fragmento más grande (valorada al considerar 100-m de perturbación al borde del fragmento) de 6, 114 a 351 ha en la zona costera, y un desbalance geográfico en los bosques protegidos con una evidente mayoría en la zona montañosa. Estos resultados demuestran una perturbación profunda de la configuración del paisaje de bosque natural y una conectividad interrumpida, lo que presenta un reto para el establecimiento de una infraestructura verde funcional. Nuestro enfoque sustenta la identificación de bosques para su protección expandida y la restauración del paisaje de bosque orientada hacia la conservación. 森林皆伐造成的自然森林丧失被认为是全世界面胳的重要保护挑战。功能性绿色基础设施是提高生物多 样性、保护状况和生态系统服务的时空上连接的景观尺度生境网络 本研究关注其建设中的森林破碎化和森林 丧失同题。通过分析卫星图像, 我们评估7\"芬诺斯坎通亚 (Fennoscancdia) 北部波的尼亚湾 (Gulf of Bothnia) 到 斯堪的纳维亚山脉(Scandinavian Mountain Range)大面积有代表性的自然和接近自然的北方森林受到 50-60 年森林皆伐的影响轨迹。这一时间段大致包括了整个森林皆伐期，因此我们的方法和结果可以应用于工业森林 管理的综合影响评估。整个研究区域覆盖了近紙000平方公里以森林为主的景風处于自然或接近自然的景 观向人为改造的土地利用类型过渡的后期。我们发现原始森林严重丧失，特别是大面积的连续区域，_ 余的森林 在区域尺度上发生空间的两极分化，其中内陆比山区和沿海地区受到更为严重的影响，内部森林核心区也受到明 显影响。突出的结果包括:山区最大的原始森林斑块面积从225,853公顷减少到 68,714 公埂而在山麓地区 从 257,715 公現滅少到38,668 公埂, 内陆地区从 75% 减少到 38%, 最大的斑块核心区域面积减少(根据 6,114 公顷到 351 公顷的沿海地区 100 米斑块边缘干扰的评估结果X 以及受保护森林的地理分布不平衡(主要在山 区) 。这些结果表明，自然森林景观配置受到严重干抵连接度受到破坏，这对建设功能性绿色基础设施提出了 挑战。我们的方法有助于确定扩大保护及进行保护导向的森林景观恢复的森林范围。

Theory predicts widespread loss of genetic diversity from drift and inbreeding in trees subjected to habitat fragmentation, yet empirical support of this theory is scarce. We argue that population genetics theory may be misapplied in light of ecological realities that, when recognized, require scrutiny of underlying evolutionary assumptions. One ecological reality is that fragment boundaries often do not represent boundaries for mating populations of trees that benefit from long-distance pollination, sometimes abetted by long-distance seed dispersal. Where fragments do not delineate populations, genetic theory of small populations does not apply. Even in spatially isolated populations, where genetic theory may eventually apply, evolutionary arguments assume that samples from fragmented populations represent trees that have had sufficient time to experience drift, inbreeding, and ultimately inbreeding depression, an unwarranted assumption where stands in fragments are living relicts of largely unrelated predisturbance populations. Genetic degradation may not be as important as ecological degradation for many decades following habitat fragmentation. /// La teoría predice una gran pérdida de diversidad genética por deriva y endogamia de árboles sujetos a la fragmentación de hábitat; sin embargo, el soporte empírico de esta teoría es escaso. Argumentamos que la teoría de la genética de poblaciones puede ser mal aplicada a la luz de realidades ecológicas que, al ser reconocidas, requieren del escrutinio de los supuestos evolutivos subyacentes. Una realidad ecológica es que los límites de los fragmentos a menudo no representan los límites para las poblaciones de árboles que se benefician con la polinización a larga distancia, a veces favorecida por la dispersión de semillas a larga distancia. Donde los fragmentos no delinean poblaciones, la teoría genética de las poblaciones pequeñas no aplica. Aun en poblaciones espacialmente aisladas, donde la teoría genética eventualmente puede aplicar, los argumentos evolutivos asumen que las muestras de poblaciones fragmentadas representan árboles que han tenido suficiente tiempo para experimentar deriva, endogamia y, finalmente, depresión por endogamia, una suposición que carece de base y donde los individuos de los fragmentos son relictos vivientes de poblaciones no emparentadas antes de la perturbación. La degradación genética puede no ser tan importante como la degradación ecológica durante muchas décadas después de la fragmentación del hábitat.

Tropical forests are experiencing enormous threats from deforestation and habitat degradation. Much knowledge of the impacts of these land-use changes on tropical species comes from studies examining patterns of richness and abundance. Demographic vital rates (survival, reproduction, and movement) can also be affected by land-use change in a way that increases species vulnerability to extirpation, but in many cases these impacts may not be manifested in short-term changes in abundance or species richness. We conducted a literature review to assess current knowledge and research effort concerning how land-use change affects species vital rates in tropical forest vertebrates. We found a general paucity of empirical research on demography across taxa and regions, with some biases toward mammals and birds and land-use transitions, including fragmentation and agriculture. There is also considerable between-species variation in demographic responses to land-use change, which could reflect trait-based differences in species sensitivity, complex context dependencies (e.g., between-region variation), or inconsistency in methods used in studies. Efforts to improve understanding of anthropogenic impacts on species demography are underway, but there is a need for increased research effort to fill knowledge gaps in understudied tropical regions and taxa. The lack of information on demographic impacts of anthropogenic disturbance makes it difficult to draw definite conclusions about the magnitude of threats to tropical ecosystems under anthropogenic pressures. Thus, determining conservation priorities and improving conservation effectiveness remains a challenge. Los bosques tropicales están experimentando enormes amenazas que surgen de la deforestación y la degradación del hábitat. Una gran parte del conocimiento sobre los impactos de estos cambios en el uso de suelo sobre las especies tropicales viene de estudios que examinan los patrones de riqueza y abundancia. Las tasas vitales demográficas (supervivencia, reproducción y movimiento) también pueden verse afectadas por el cambio en el uso de suelo de una manera que incrementa la vulnerabilidad de las especies ante la extirpación, pero en la mayoría de los casos estos impactos pueden no estar manifestados como cambios a corto plazo en la abundancia o en la riqueza de especies. Realizamos una revisión de la literatura para evaluar el conocimiento actual y los esfuerzos de investigación con respecto a cómo el cambio en el uso de suelo afecta a las tasas vitales de las especies de vertebrados de los bosques tropicales. Encontramos una escasez general de investigaciones empíricas sobre la demografía en los taxones y en las regiones y algunos sesgos hacia los mamíferos, las aves y las transiciones de uso de suelo, incluyendo la fragmentación y la agricultura. También existe una variación considerable entre especies en las respuestas demográficas al uso de suelo, lo que podría reflejar diferencias basadas en las características en la sensibilidad de las especies, dependencias complejas por el contexto (p. ej.: variación entre regiones), o inconsistencias en los métodos utilizados para los estudios. Los esfuerzos por mejorar el entendimiento de los impactos antropogénicos sobre la demografía de las especies están realizándose, pero existe una necesidad de un mayor esfuerzo de investigación para llenar los vacíos de conocimiento en los taxones y en las regiones tropicales poco estudiadas. La falta de información sobre los impactos demográficos de las perturbaciones antropogénicas complica la formulación de conclusiones definitivas sobre la magnitud de las amenazas que presentan los ecosistemas tropicales bajo presiones antropogénicas. Por ello, todavía es un reto determinar las prioridades de conservación y mejorar la efectividad de la conservación. 热带森林芷面临森林砍伐和栖息地退化的严重威胁。对于这些土地利用变化影响热带物种的认识主要来 自丰富度和丰度格局的研究。然而，物种的种群生命率（存活率、繁殖率和迁移）也可能受到土地利用变化的影 喊使物种面临更高的灭绝风险，旦在许多情况下这些影响难以体现在物种丰度或丰富度的短期变化中。我们通 过文献综述评估了关于土地利用变化如何影响热带森林脊椎动物生命率的已有知识和研究工作。我们发现，跨 类群和跨地区的种群统计实钲研究普遍缺乏，更多研究关注哺乳动物、鸟类和土地利用的转变，包括碎片化和农 业开发。种群统计参数对土地利用变化的响应存在明显的物种间差异，这可能反映了基于特性的物种敏感性以 及复杂的情景依赖性_ 区域间差异），抑或是研究方法的不一致。虽然在深人理解人类活动対物种种群参数影 响的方面已有不少努力，但仍需加大研究力度来填补热带地区和类群知识的空缺。由于缺乏人类干扰对种群影 响的认识，我们狼难就人为压カ对热带生态系统造成威胁的程度得出明确定论。因此，确定保护优先性并提高保 护有效性仍然是ー项挑战

It is important for conservation biologists to understand how well species persist in human-dominated ecosystems because protected areas constitute a small fraction of the Earth's surface and because anthropogenic habitats may offer more opportunities for conservation than has been previously thought. We investigated how an important functional group, pollinators (bees; Hymenoptera: Apiformes), are affected by human land use at the landscape and local scales in southern New Jersey (U.S.A.). We established 40 sites that differed in surrounding landscape cover or local habitat type and collected 2551 bees of 130 species. The natural habitat in this ecosystem is a forested, ericaceous heath. Bee abundance and species richness within forest habitat decreased, not increased, with increasing forest cover in the surrounding landscape. Similarly, bee abundance was greater in agricultural fields and suburban and urban developments than in extensive forests, and the same trend was found for species richness. Particular species groups that might be expected to show greater sensitivity to habitat loss, such as floral specialists and bees of small or large body size, did not show strong positive associations with forest habitat. Nevertheless, 18 of the 130 bee species studied were positively associated with extensive forest. One of these species is a narrow endemic that was last seen in 1939. Our results suggest that at least in this system, moderate anthropogenic land use may be compatible with the conservation of many, but not all, bee species.

Few researchers have investigated the synergistic effects of tropical forest fragmentation and disturbance on species persistence and abundance. We examined effects of both forest-patch metrics and forest disturbance in determining richness and abundance of midsized to large-bodied mammal species in a highly fragmented Amazonian forest landscape. Twenty-one forest fragments, ranging from 2 to 14,480 ha, and two continuous forest sites were sampled based on sightings, tracks, line-transect censuses, armadillo burrow censuses, and camera trapping. Patch occupancy of 37 species recorded ranged from 4% to all forest sites surveyed. Forest fragment size was the strongest predictor of species persistence, explaining 90% of the variation in species richness. Information-theoretic analysis confirmed that fragment area was the most important explanatory variable for the overall species richness and abundance of mammal species, followed by surface fires, which affected the abundance of seven species. Large mammal species were typically absent from fragments <100 ha, whereas some ubiquitous species were favored by fragmentation, exhibiting hyperabundance in small patches. Our findings highlight the importance of large (>10,000 ha), relatively undisturbed forest patches to maximize persistence and maintain baseline abundances of Neotropical forest mammal species.

Despite many studies on fragmentation of tropical forests, the extent to which plant and animal communities are altered in small, isolated forest fragments remains obscure if not controversial. We examined the hypothesis that fragmentation alters the relative abundance of tree species with different vegetative and reproductive traits. In a fragmented landscape (670 km²) of the Atlantic Forest of northeastern Brazil, we categorized 4056 trees of 182 species by leafing pattern, reproductive phenology, and morphology of seeds and fruit. We calculated relative abundance of traits in 50 1‐ha plots in three types of forest configurations: forest edges, small forest fragments (3.4-83.6 ha), and interior of the largest forest fragment (3500 ha, old growth). Although evergreen species were the most abundant across all configurations, forest edges and small fragments had more deciduous and semideciduous species than interior forest. Edges lacked supra‐annual flowering and fruiting species and had more species and stems with drupes and small seeds than small forest fragments and forest interior areas. In an ordination of species similarity and life‐history traits, the three types of configurations formed clearly segregated clusters. Furthermore, the differences in the taxonomic and functional (i.e., trait‐based) composition of tree assemblages we documented were driven primarily by the higher abundance of pioneer species in the forest edge and small forest fragments. Our work provides strong evidence that long‐term transitions in phenology and seed and fruit morphology of tree functional groups are occurring in fragmented tropical forests. Our results also suggest that edge‐induced shifts in tree assemblages of tropical forests can be larger than previously documented.

Housing growth and its environmental effects pose major conservation challenges. We sought to (1) quantify spatial and temporal patterns of housing growth across the U.S. Midwest from 1940-2000, (2) identify ecoregions strongly affected by housing growth, (3) assess the extent to which forests occur near housing, and (4) relate housing to forest fragmentation. We used data front the 2000 U.S. Census to derive fine-scale backcasts of decadal housing density. Housing data were integrated with a 30-m resolution U.S. Geological Survey land cover classification. The number of housing units in the Midwest grew by 146% between 1940 and 2000. Spatially, housing growth was particularly strong at the fringe of metropolitan areas (suburban sprawl) and in nonmetropolitan areas (rural sprawl) that are rich in natural amenities such as lakes and forests. The medium-density housing (4-32 housing units/km2) category increased most in area. Temporally, suburban housing growth was especially high in the post-World War II decades. Rural sprawl was highest in the 1970s and 1990s. The majority of midwestern forests either contained or were near housing. Only 14.8% of the region's forests were in partial block groups with no housing. Housing density was negatively correlated with the amount of interior forest. The widespread and pervasive nature of sprawl shown by our data is cause for conservation concern. Suburban sprawl has major environmental impacts on comparatively small areas because of the high number of housing units involved. In contrast, rural sprawl affects larger areas but with less intensity because associated housing densities are lower. The environmental effects per house, however, are likely higher in the case of rural sprawl because it occurs in less-altered areas. Conservation efforts will need to address both types of sprawl to be successful.

Most amphibian species have biphasic life histories and undergo an ontogenetic shift from aquatic to terrestrial habitats. In deforested landscapes, streams and forest fragments are frequently disjunct, jeopardizing the life cycle of forest-associated amphibians with aquatic larvae. We tested the impact of habitat split--defined as human-induced disconnection between habitats used by different life-history stages of a species--on four forest-associated amphibian species in a severely fragmented landscape of the Brazilian Atlantic Forest. We surveyed amphibians in forest fragments with and without streams (referred to as wet and dry fragments, respectively), including the adjacent grass-field matrix. Our comparison of capture rates in dry fragments and nearby streams in the matrix allowed us to evaluate the number of individuals that engaged in high-risk migrations through nonforested habitats. Adult amphibians moved from dry fragments to matrix streams at the beginning of the rainy season, reproduced, and returned at the end of the breeding period. Juveniles of the year moved to dry fragments along with adults. These risky reproductive migrations through nonforested habitats that expose individuals to dehydration, predation, and other hazards may cause population declines in dry fragments. Indeed, capture rates were significantly lower in dry fragments compared with wet fragments. Declining amphibians would strongly benefit from investments in the conservation and restoration of riparian vegetation and corridors linking breeding and nonbreeding areas.

Forest fragmentation is a leading driver of biodiversity loss, yet its effects on positive species interactions remain poorly known. We examined the effects of fragmentation on mixed-species bird flocks in the Western Andes of Colombia. Using 500-m transect surveys (n = 14 transects), we sampled flocks in 8 fragments (range: 10–173 ha) and an unfragmented reference site within the same altitudinal band (1,900–2,200 m.a.s.l.) and matrix type (cattle pasture). We evaluated the relative contributions of 9 predictor variables, including patch size, distance from edge, and selective aspects of vegetation structure on the composition, size, species richness, functional diversity, and phylogenetic diversity of flocks. We found effects of both patch size and vegetation structure on flock species richness, size, and functional diversity, but no support for edge effects. Generally, flock richness and size responded differently to fragmentation than did functional and phylogenetic diversity metrics. Both flock size and richness increased with patch size, but this variable had no effect on functional and phylogenetic diversity. Flock richness and size increased in high-canopy forests with greater foliage height diversity, whereas unlogged, old-growth primary forests with large-diameter trees had lower flock richness and size, but significantly greater functional diversity. Phylogenetic diversity was not affected by patch size, edge effects, or vegetation structure. We found differences in flock composition in response to fragmentation. Richness of Furnariidae in flocks increased with increasing distance from edge and foliage height diversity, whereas that of Thraupidae and boreal migrant species increased in early successional and forest edge flocks, respectively. All flock diversity metrics differed significantly seasonally, with smaller, less diverse flocks observed in January–March than in June–August. Flocking behavior persisted in 10-ha fragments, likely because Andean flocks are ″open membership” in nature, but there was extensive species turnover as forest edge and generalist species replaced forest-interior species in smaller fragments.