Ecological Applications

Anthropogenic features such as urbanization, roads, and power lines, are increasing in western United States landscapes in response to rapidly growing human populations. However, their spatial effects have not been evaluated. Our goal was to model the human footprint across the western United States. We first delineated the actual area occupied by anthropogenic features, the physical effect area. Next, we developed the human footprint model based on the ecological effect area, the zone influenced by features beyond their physical presence, by combining seven input models: three models quantified top‐down anthropogenic influences of synanthropic predators (avian predators, domestic dog and cat presence risk), and four models quantified bottom‐up anthropogenic influences on habitat (invasion of exotic plants, human‐caused fires, energy extraction, and anthropogenic wildland fragmentation). Using independent bird population data, we found bird abundance of four synanthropic species to correlate positively with human footprint intensity and negatively for three of the six species influenced by habitat fragmentation. We then evaluated the extent of the human footprint in relation to terrestrial (ecoregions) and aquatic systems (major rivers and lakes), regional management and conservation status, physical environment, and temporal changes in human actions. The physical effect area of anthropogenic features covered 13% of the western United States with agricultural land (9.8%) being most dominant. High‐intensity human footprint areas (class 8–10) overlapped highly productive low‐elevation private landholdings and covered 7% of the western United States compared to 48% for low‐intensity areas (class 1–3), which were confined to low‐productivity high‐elevation federal landholdings. Areas within 1 km of rivers were more affected by the human footprint compared to lakes. Percentage human population growth was higher in low‐intensity human footprint areas. The disproportional regional effects of the human footprint on landscapes in the western United States create a challenge to management of ecosystems and wildlife populations. Using footprint models, managers can plan land use actions, develop restoration scenarios, and identify areas of high conservation value at local landscapes within a regional context. Moreover, human footprint models serve as a tool to stratify landscapes for studies investigating floral and faunal response to human disturbance intensity gradients.

Deploying well‐adapted and ecologically appropriate plant materials is a core component of successful restoration projects. We have developed generalized provisional seed zones that can be applied to any plant species in the United States to help guide seed movement. These seed zones are based on the intersection of high‐resolution climatic data for winter minimum temperature and aridity (as measured by annual heat : moisture index), each classified into discrete bands. This results in the delineation of 64 provisional seed zones for the continental United States. These zones represent areas of relative climatic similarity, and movement of seed within these zones should help to minimize maladaptation. Superimposing Omernik's level III ecoregions over these seed zones distinguishes areas that are similar climatically yet different ecologically. A quantitative comparison of provisional seed zones with level III ecoregions and provisional seed zones within ecoregions for three species showed that provisional seed zone within ecoregion often explained the greatest proportion of variation in a suite of traits potentially related to plant fitness. These provisional seed zones can be considered a starting point for guidelines for seed transfer, and should be utilized in conjunction with appropriate species‐specific information as well as local knowledge of microsite differences.

Genetic resources have to be managed appropriately to mitigate the impact of climate change. For many wildland plants, conservation will require knowledge of the climatic factors affecting intraspecific genetic variation to minimize maladaptation. Knowledge of the interaction between traits and climate can focus management resources on vulnerable populations, provide guidance for seed transfer, and enhance fitness and resilience under changing climates. In this study, traits of big sagebrush (Artemisia tridentata) were examined among common gardens located in different climates. We focus on two subspecies,wyomingensisandtridentata, that occupy the most imperiled warm‐dry spectrum of the sagebrush biome. Populations collected across the sagebrush biome were recorded for flower phenology and survival. Mixed‐effects models examined each trait to evaluate genetic variation, environmental effects, and adaptive breadth of populations. Climate variables derived from population‐source locations were significantly associated with these traits (P < 0.0001), explaining 31% and 11% of the flower phenology and survival variation, respectively. To illustrate our model and assess variability in prediction, we examine fixed and focal point seed transfer approaches to map contemporary and climate model ensemble projections in two different regions of the sagebrush biome. A comparison of seed transfer areas predicts that populations from warmer climates become more prevalent, replacing colder‐adapted populations by mid‐century. However, these warm‐adapted populations are often located along the trailing edge, margins of the species range predicted to be lost due to a contraction of the climatic niche. Management efforts should focus on the collection and conservation of vulnerable populations and prudent seed transfer to colder regions where these populations are projected to occur by mid‐century. Our models provide the foundation to develop an empirical, climate‐based seed transfer system for current and future restoration of big sagebrush.

Các cộng đồng thực vật, vỏ đất sinh học (BSCs) và nấm mycorrhiza arbuscular (AM) được biết đến là có ảnh hưởng đến độ ổn định của đất một cách riêng lẻ, nhưng những đóng góp tương đối, các tương tác và ảnh hưởng kết hợp của chúng chưa được hiểu rõ, đặc biệt là trong các hệ sinh thái khô hạn và bán khô hạn. Trong một nghiên cứu trên quy mô cảnh quan, chúng tôi đã thu thập dữ liệu về cộng đồng thực vật, BSC và nấm AM tại 216 địa điểm dọc theo gradient độ ổn định của đất ở phía nam Utah, Hoa Kỳ. Chúng tôi đã sử dụng mô hình đa biến để kiểm tra ảnh hưởng tương đối của thực vật, BSCs và nấm AM đến độ ổn định bề mặt và dưới bề mặt trong một cảnh quan cây bụi bán khô hạn. Các mô hình được phát hiện là phù hợp với dữ liệu và giải thích 35% sự biến động trong độ ổn định bề mặt và 54% sự biến động trong độ ổn định dưới bề mặt. Kết quả hỗ trợ một số kết luận tạm thời. Trong khi BSCs, thực vật và nấm AM đều đóng góp vào độ ổn định bề mặt, chỉ có thực vật và nấm AM đóng góp vào độ ổn định dưới bề mặt. Trong cả hai mô hình bề mặt và dưới bề mặt, những đóng góp mạnh nhất vào độ ổn định của đất đến từ các thành phần sinh học của hệ thống. Đặc biệt, lớp vỏ đất sinh học được phát hiện có ảnh hưởng trực tiếp mạnh nhất đến độ ổn định của đất bề mặt (0.60; kiểm soát các yếu tố khác). Ngạc nhiên, nấm AM dường như ảnh hưởng đến độ ổn định của đất bề mặt (0.37), mặc dù chúng không thường được coi là tồn tại ở vài milimét đầu tiên của đất. Trong mô hình dưới bề mặt, lớp thực vật dường như có ảnh hưởng trực tiếp mạnh nhất đến độ ổn định của đất (0.42); trong cả hai mô hình, kết quả chỉ ra rằng lớp thực vật ảnh hưởng đến độ ổn định của đất cả trực tiếp (kiểm soát các yếu tố khác) và gián tiếp thông qua ảnh hưởng lên các sinh vật khác. Chất hữu cơ trong đất không được tìm thấy có đóng góp trực tiếp đến độ ổn định bề mặt hoặc dưới bề mặt trong hệ thống này. Ảnh hưởng tương đối của nấm AM đến độ ổn định của đất trong các khu vực cây bụi bán khô hạn này tương tự như những gì được báo cáo cho một đồng cỏ cỏ cao mesic. Các ước tính về ảnh hưởng mà BSCs, thực vật và nấm AM có đến độ ổn định của đất trong các mô hình này được sử dụng để đề xuất số lượng tương đối tài nguyên mà các chuyên gia kiểm soát xói mòn nên dành để thúc đẩy các cộng đồng này. Nghiên cứu này làm nổi bật nhu cầu về các phương pháp hệ thống trong việc chống lại xói mòn, suy thoái đất và sa mạc hóa đất khô.

In November 2015, a large mine‐tailing dam owned by Samarco Corporation collapsed in Brazil, generating a massive wave of toxic mud that spread down the Doce River, killing 20 people and affecting biodiversity across hundreds of kilometers of river, riparian lands, and Atlantic coast. Besides the disaster's serious human and socioeconomic tolls, we estimate the regional loss of environmental services to be ~US$521 million per year. Although our estimate is conservative, it is still six times higher than the fine imposed on Samarco by Brazilian environmental authorities. To reduce such disparities between estimated damages and levied fines, we advocate for an environmental bond policy that considers potential risks and environmental services that could possibly be impacted by irresponsible mining activity. Environmental bonds and insurance are commonly used policy instruments in many countries, but there are no clear environmental bond policies in Brazil. Environmental bonds are likely to be more effective at securing environmental restitution than post‐disaster fines, which generally are inadequate and often unpaid. We estimate that at least 126 mining dams in Brazil are vulnerable to failure in the forthcoming years. Any such event could have severe social‐environmental consequences, underscoring the need for effective disaster‐management strategies for large‐scale mining operations.

We use a graph‐theoretical landscape modeling approach to investigate how to identify central patches in the landscape as well as how these central patches influence (1) organism movement within the local neighborhood and (2) the dispersal of organisms beyond the local neighborhood. Organism movements were theoretically estimated based on the spatial configuration of the habitat patches in the studied landscape. We find that centrality depends on the way the graph‐theoretical model of habitat patches is constructed, although even the simplest network representation, not taking strength and directionality of potential organisms flows into account, still provides a coarse‐grained assessment of the most important patches according to their contribution to landscape connectivity. Moreover, we identify (at least) two general classes of centrality. One accounts for the local flow of organisms in the neighborhood of a patch, and the other accounts for the ability to maintain connectivity beyond the scale of the local neighborhood. Finally, we study how habitat patches with high scores on different network centrality measures are distributed in a fragmented agricultural landscape in Madagascar. Results show that patches with high degree and betweenness centrality are widely spread, while patches with high subgraph and closeness centrality are clumped together in dense clusters. This finding may enable multispecies analyses of single‐species network models.

I examined the distribution and abundance of bird species across an urban gradient, and concomitant changes in community structure, by censuring summer resident bird populations at six sites in Santa Clara County, California (all former oak woodlands). These sites represented a gradient of urban land use that ranged from relatively undisturbed to highly developed, and included a biological preserve, recreational area, golf course, residential neighborhood, office park, and business district. The composition of the bird community shifted from predominantly native species in the undisturbed area to invasive and exotic species in the business district. Species richness, Shannon diversity, and bird biomass peaked at moderately disturbed sites. One or more species reached maximal densities in each of the sites, and some species were restricted to a given site. The predevelopment bird species (assumed to be those found at the most undisturbed site) dropped out gradually as the sites became more urban. These patterns were significantly related to shifts in habitat structure that occurred along the gradient, as determined by canonical correspondence analysis (CCA) using the environmental variables of percent land covered by pavement, buildings, lawn, grasslands, and trees or shrubs. I compared each formal site to four additional sites with similar levels of development within a two‐country area to verify that the bird communities at the formal study sites were representative of their land use category.