海南岛淡水蟹类分布格局与多样性保护

热带岛屿生物多样性是全球生物多样性保护研究的热点之一。海南岛是中国面积最大的热带岛屿, 丰富独特的淡水蟹类是维持岛内淡水生态系统功能完整性的关键类群。本文通过多年野外调查, 综合历史及最新文献资料, 对海南岛淡水蟹类物种多样性及其现状进行调查和评估, 并对淡水蟹类物种多样性保护现状进行了分析讨论。研究发现, 海南岛淡水蟹类物种多样性分布中心位于中南部山地, 主要集中于中部的霸王岭、鹦哥岭和猕猴岭, 南部的五指山和吊罗山, 以及西南部的尖峰岭一带。其物种多样性整体上呈现中南部山地高、平原台地低的特点。根据《IUCN物种红色名录濒危等级和标准》对海南岛淡水蟹类物种现状的评估结果显示, 全岛受威胁淡水蟹类物种的占比为16.7%。基于分布区预测, 以海南热带雨林国家公园为主体的保护地对淡水蟹类潜在适宜分布区的覆盖度明显优于此前碎片化的各级保护区。本文研究结果显示, 海南岛淡水蟹类的总体生存状况良好, 但一部分山地或平原种类处于受胁状态。国家公园体制的建立有望为岛内淡水蟹类物种多样性保护提供前所未有的机遇。基于物种多样性分布格局开展淡水蟹类等淡水生物多样性监测, 有助于促进海南岛淡水生态系统完整性的长效保护与可持续发展。     

Biodiversity conservation in Changbai Mountain Biosphere Reserve, northeastern China: status, problem, and strategy

The Changbai Mountain Biosphere Reserve (CMBR) is the largest and one of the earliest natural reserves established in China. The continuous losses of species and ecosystems in the reserve since its establishment have raised numerous concerns within China and beyond, which also leads some people to question the function and efficiency of natural reserves in protecting biological and ecological resources. By collecting the published data, conducting field investigation, and interviewing local people, we present the current status of biological and ecological diversity/resources in the reserve and analyze the major factors causing biodiversity loss in the reserve in an ecological and socio-economic context. We found that the high human population pressure, mismanagement practices of resources, a poor resource evaluation system which underestimates the ecological value of the natural reserve, an inappropriate economic development policy, and rapid expansion of the tourist industry were the major causes leading to the biodiversity loss in the reserve in the past few decades. In order to manage the biological resources and biodiversity in the CMBR in a sustainable way, we recommend some strategies and measures which include balancing economic development and biological/ecological conservation, controlling human population in the reserve, encouraging collaboration within and outside the reserve, especially the areas around the reserve, enhancing governmental assistance and subsidy to the local residents, and promoting scientific research and biodiversity education in the local communities.     

自然保护区生态安全设计的方法研究

由于生态破坏和自然栖息地的丧失,造成野生动植物种群的破碎化．自然保护区已成为孤立的生境岛屿,目前以单个、孤立保护区为主的生物多样性保护模式是远远不够的,应在广泛的时空尺度上保护生态过程和生物多样性各组成成份,建立一个整体的保护网络．根据国内外生物多样性保护的要求和发展趋势,提出了自然保护区生态安全设计的概念,它是综合考虑了生态、社会、经济的一种协调设计战略,首先从区域层次研究保护区网络的优化设计;其次,在网络的每个节点(保护区),研究保护区的面积、形状和内部功能分区;最后,研究网络与节点的连接(廊道)．自然保护区网络设计应维持生态系统的地域完整性和生态过程完整性,采用迭代法、整数规划方法和地理途径方法,为一个或多个保护目标勾画出多种保护规划蓝图。     

中国生物多样性就地保护成效与展望

生物多样性就地保护是指通过开展自然保护地体系的建立与管理, 结合自然保护地以外其他有效的基于区域的保护措施(other effective area-based conservation measures, OECMs), 从而实现物种种群及其栖息地的保护与恢复以及保障和提升生态系统服务的目标。就地保护是实现2020年全球生物多样性保护目标最为重要的措施之一。本文从自然保护地数量与面积、代表性、有效性, 以及其他生物多样性就地保护措施等方面, 整理和综述了国内外近年来的相关报道。总体来看, 我国基本建立了具有中国特色的生物多样性就地保护与管理体系, 实施了各项生物多样性保护恢复措施, 取得了一系列重大进展。自然保护地的面积和数量均呈现上升趋势, 已覆盖陆域国土面积的18%, 对一些重要生态系统及重点保护物种的保护取得了一定成效。正在建设的10处国家公园体制试点提升了部分重点物种的保护连通性。自然保护区总体管理状况相对较好, 保护了90%以上的哺乳动物和97%的兰科植物。此外, 其他有效的基于区域的保护措施亦为生物多样性就地保护贡献了民间力量。在此基础上, 本文对照《中国生物多样性保护战略与行动计划(2011-2030年)》中对“加强生物多样性就地保护”的各项要求, 分析总结了当前我国生物多样性就地保护仍然存在的问题与不足, 具体表现在以下几个方面: 自然保护地整体保护能力仍有待提升; 生物多样性保护优先区域仍然存在保护空缺; 自然保护区管理质量有待提升; 缺乏公共协商机制; 自然保护地以外的其他就地保护工作仍在探索阶段等。在此基础上, 对将来我国生物多样性就地保护提出了进一步建议与展望: (1)制定更为具体和量化的生物多样性就地保护目标; (2)加大力度减少物种受威胁程度, 特别是受关注较少的物种; (3)以保障和提升生态系统服务为目标, 提升生态系统保护修复的系统性与整体性; (4)加强自然保护地以外的生物多样性就地保护; (5)完善长期监测体系, 为生物多样性就地保护成效评估提供数据支撑。本文可为“2020年后全球生物多样性框架”特别是就地保护目标的制定与实施提供参考。     

自然保护地保护成效评估: 进展与展望

自然保护地(protected areas)保护成效是指自然保护地对主要保护对象的保护效果, 及其在维持生物多样性和保障生态系统服务功能等方面的综合成效。近年来自然保护地保护成效评估逐渐成为国内外的研究热点之一。 本文分别从不同空间尺度、评估对象、评估方法以及评估指标等方面综述了相关的研究进展。总体来看, 近年来的研究已基本覆盖了全球、区域、国家和单个自然保护地等不同尺度, 针对森林、湿地、草地和荒漠等代表性生态系统以及野生动植物等主要保护对象进行了评估, 发展了“matching”技术等更为有效的分析方法, 探索了系统的自然保护地保护成效评估指标体系, 并应用一些指标进行了保护成效的案例研究。自然保护区(nature reserve)是我国自然保护地的主体, 近年来我国自然保护区相关管理部门也相继开展了保护成效评估工作, 建议未来进一步加强自然保护区网络尺度和各类型自然保护区的保护成效评估研究, 将自然保护区保护成效评估与管理评估相结合, 研究自然保护区保护成效面临的新问题和潜在影响, 为提升我国自然保护区管理质量提供科学依据。     

Rapid increase in fish numbers follows creation of world's largest marine reserve network

No-take marine reserves (NTMRs) are much advocated as a solution to managing marine ecosystems, protecting exploited species and restoring natural states of biodiversity [1,2]. Increasingly, it is becoming clear that effective marine conservation and management at ecosystem and regional scales requires extensive networks of NTMRs [1,2]. The world's largest network of such reserves was established on Australia's Great Barrier Reef (GBR) in 2004. Closing such a large area to all fishing has been socially and politically controversial, making it imperative that the effectiveness of this new reserve network be assessed. Here we report evidence, first, that the densities of the major target species of the GBR reef line fisheries were significantly higher in the new NTMRs, compared with fished sites, in just two years; and second, that the positive differences were consistent for multiple marine reserves over an unprecedented spatial scale (>1,000 km).     

中国红树林生态系统保护空缺分析

红树林作为海岸带重要的生态系统类型,具有维持海岸生物多样性、防风固岸、促淤造陆等重要的生态功能,在气候变化和快速城市化背景下认识红树林受保护状况具有重要意义。以基于遥感解译的红树林分类数据为基础,通过空缺分析,分析了我国红树林的就地保护状况,结果显示我国分布的红树林总面积为264 km~2(尚不含我国港、澳、台的统计数据),其中61.4%在自然保护区内受到保护。从红树林分布的主要省份来看,在海南省分布的红树林面积较少但保护比例高,广西和广东省分布的红树林面积大但受保护面积比例相对较低。在3种红树林类型中,红树-木果楝林和红海榄-木榄林分布面积较小,但受保护的面积都在90%以上,秋茄-桐花树-白骨壤林分布的面积最大,但受保护的面积为52.6%。研究提出自然保护区外红树林分布的关键区域,并建议通过划定生态保护红线等方式来进行保护。     

Comparison of biodiversity and ground cover between a commercial rotationally grazed property and an adjacent nature reserve in semi‐arid rangeland

Continuous livestock grazing can have negative effects on biodiversity and landscape function in arid and semi‐arid rangelands. Alternative grazing management practices, such as rotational grazing, may be a viable option for broad‐scale biodiversity conservation and sustainable pastoral management. This study compared ground cover, plant species composition and floristic and functional diversity along gradients of grazing intensity between a pastoral property rotationally grazed by goats and an adjacent nature reserve (ungrazed by commercial livestock) in semi‐arid south‐eastern Australia. Understorey plant species composition differed significantly between the rotationally grazed property and the nature reserve, with a greater proportion and frequency of palatable species recorded in the nature reserve. Understorey plant species richness, diversity, functional biodiversity measures and ground cover declined with increasing grazing pressure close to water points under commercial rotational grazing management. However, at a whole‐paddock scale, there were few differences in plant biodiversity and ground cover between the rotationally grazed property and the nature reserve, despite differences in overall plant species composition. Flexible, adaptive, rotational grazing should be investigated further for its potential to achieve both socio‐economic and biodiversity conservation outcomes in semi‐arid rangelands to complement existing conservation reserves.     

A method for spatial freshwater conservation prioritization

1. Freshwater ecosystems are amongst the most threatened and poorly protected globally. They continue to be degraded through habitat loss, pollution and invading species and conservation measures are urgently needed to halt declining trends in their biodiversity and integrity.
2. During the past decade a suite of decision support tools and computational approaches have been developed for efficient and targeted conservation action in terrestrial or marine ecosystems. These methods may be poorly suited for planning in freshwater systems because connectivity in terrestrial and marine systems is typically modelled in a way unsuitable for rivers, where connectivity has a strong directional component.
3. We modify the conservation prioritization method and software, zonation , to account for connectivity in a manner better suited to freshwater ecosystems. Prioritization was performed using subcatchment/catchment-based planning units and connectivity was modified to have directional upstream and downstream components consistent with the ecology of our target species.
4. We demonstrate this modified method for rivers and streams in the southern North Island of New Zealand. Data included predicted occupancy from boosted regression tree models of species distributions for 18 fish species. The study area covered 2.1 million hectares and included 394 first- to fourth order catchment or subcatchment planning units.
5. Realistic modelling of connectivity had a major influence on the areas proposed for conservation. If connectivity was ignored, recommended conservation areas were very fragmented. By contrast, when connectivity was modelled, high priority conservation targets consisted of entire river basins or headwater subcatchments.
6. The proposed method serves as a starting point for the implementation of reserve selection methods in river ecosystems.     

Synthesizing the role of epigenetics in the response and adaptation of species to climate change in freshwater ecosystems

Freshwater ecosystems are amongst the most threatened ecosystems on Earth. Currently, climate change is one of the most important drivers of freshwater transformation and its effects include changes in the composition, biodiversity and functioning of freshwater ecosystems. Understanding the capacity of freshwater species to tolerate the environmental fluctuations induced by climate change is critical to the development of effective conservation strategies. In the last few years, epigenetic mechanisms were increasingly put forward in this context because of their pivotal role in gene–environment interactions. In addition, the evolutionary role of epigenetically inherited phenotypes is a relatively recent but promising field. Here, we examine and synthesize the impacts of climate change on freshwater ecosystems, exploring the potential role of epigenetic mechanisms in both short‐ and long‐term adaptation of species. Following this wrapping‐up of current evidence, we particularly focused on bringing together the most promising future research avenues towards a better understanding of the effects of climate change on freshwater biodiversity, specifically highlighting potential molecular targets and the most suitable freshwater species for future epigenetic studies in this context.     

Assessing the potential of a protected area for fish conservation in a neotropical wetland

Freshwater habitats are among the most impacted ecosystem on Earth. Consequently, reserves have been implemented in an attempt to reduce the threat to freshwater biodiversity. However, few studies have evaluated how effective these protected areas (PA) are for the conservation of freshwater organisms. In the present study, we compared species richness, community composition and density of small-bodied fishes between lagoons within an eight-year-old reserve (i.e. protected lagoons) with those outside the reserve (i.e. unprotected lagoons) in a river-floodplain system that is exposed to seasonal flooding. The unprotected lagoons have been submitted to a light fishing pressure mainly targeting small-sized fishes for sale as baits. Our results showed no differences between the lagoons inside the reserve with those outside in any of the community properties measured. However, we registered an overall tendency of abundance reduction among the species used as baits in unprotected lagoons. Considering the high degree of oversight in the PA and the low fishing pressure among unprotected lagoons, it is possible that the positive effects promoted by the reserve on fish assemblages are being exported towards unprotected lagoons and thus offsetting a portion of the anthropogenic impacts. We conclude that the protection provided by the reserve is very efficient in river-floodplain systems, because not only it protects the biota inside the reserve but also act as a source of propagules to unprotected areas during the rainy season when all the aquatic subsystems are connected by the flood.     

国家级自然保护区生态系统格局十年变化(2000-2010年)评估

为揭示国家级自然保护区生态系统格局构成及变化状况,基于2000年和2010年319个国家级自然保护区生态系统类型与分布数据,根据生态系统类型转化及其转化幅度,考虑自然保护区各功能区的重要性,构建生态系统格局变化指数,分析国家级自然保护区生态系统格局动态变化。结果表明,国家级自然保护区草地生态系统面积最大,2000年和2010年分别占全国国家级自然保护区总面积的57.88%和57.74%,其次为荒漠生态系统,两期占比约17%,其他依次是湿地、森林、灌丛、农田、冰川/永久积雪、海洋、城镇等生态系统类型。2000-2010年,国家级自然保护区内森林、湿地面积明显增加,城镇有一定程度扩张,冰川/永久积雪略微减少。总体上,国家级自然保护区生态系统格局基本保持稳定,基本维持的保护区数量219个,占国家级自然保护区总数的68.65%,生态系统格局改善的保护区数量略多于退化的数量,10年来国家级自然保护区生态系统格局保护取得一定效果。国家级自然保护区生态系统格局在基本维持的基础上,表现出一定的地域不平衡性。生态系统改善的保护区多分布在秦岭、大巴山、大娄山、南岭一带,而东部省份、内蒙古高原、东北平原一带生态系统退化的保护区数量较多,主要是荒漠、内陆湿地和水域、野生动物、自然遗迹等类型自然保护区。最后,提出3点建议为提高国家级自然保护区管理水平提供参考。     

A comparison of marine protected areas and alternative approaches to coral-reef management

Marine protected areas (MPAs) have been widely adopted as the leading tool for coral-reef conservation, but resource users seldom accept them , and many have failed to produce tangible conservation benefits [3]. Few studies have objectively and simultaneously examined the types of MPAs that are most effective in conserving reef resources and the socioeconomic factors responsible for effective conservation [4-6]. We simultaneously explored measures of reef and socioeconomic conservation success at four national parks, four comanaged reserves, and three traditionally managed areas in Indonesia and Papua New Guinea. Underwater visual censuses of key ecological indicators [7, 8] revealed that the average size and biomass of fishes were higher in all areas under traditional management and at one comanaged reserve when compared to nearby unmanaged areas. Socioeconomic assessments [6, 9, 10] revealed that this "effective conservation" was positively related to compliance, visibility of the reserve, and length of time the management had been in place but negatively related to market integration, wealth, and village population size. We suggest that in cases where the resources for enforcement are lacking, management regimes that are designed to meet community goals can achieve greater compliance and subsequent conservation success than regimes designed primarily for biodiversity conservation.     

Evaluating reserves for species richness and representation in northern California

The Klamath‐Siskiyou forests of northern California and southern Oregon are recognized as an area of globally outstanding biological distinctiveness. When evaluated at a national or global level, this region is often, necessarily, considered to be uniformly diverse. Due to large variation in biotic and abiotic variables throughout this region, however, it is unlikely that biological diversity is uniformly distributed. Furthermore, land management decisions nearly always occur at spatial scales smaller than this entire region. Therefore, we used field data from a random sampling design to map the distribution of local and regional richness of terrestrial molluscs and salamanders within northern California's portion of the Klamath‐Siskiyou region. We also evaluated the protection afforded by reserves established for varying reasons (e.g. for inspiration and recreation for people vs. species conservation) to hotspots of species richness and species representation of these taxa. No existing reserves were created with these taxa in mind, yet it was assumed that reserves established largely around considerations for the northern spotted owl (Strix occidentalis caurina) would afford adequate protection for many lesser‐known species. Species of terrestrial molluscs and salamanders share two general features: (1) they have extremely low vagility, and (2) they are often associated with moist, cool microclimates. Existing reserves disproportionately included areas of hotspots of species richness for both taxa, when hotspots included the richest c. 25% of the area, whereas non‐reserved lands contained greater than expected areas with lower species richness. However, when a more strict definition of hotspot was used (i.e. the richest c.10% of areas), local hotspots for both taxa were not disproportionately found in reserves. Reserves set aside largely for human aesthetics and recreation and those set aside for biodiversity both contributed to the protection of areas with high (greatest 25%) species richness. Existing biodiversity reserves represented 68% of mollusc species and 73% of salamander species, corresponding to the 99th and 93rd percentiles, respectively, of species representation achieved by simulating a random distribution of the same total area of reservation. Cumulatively, however, reserves set aside for inspiration and biodiversity represented 83% of mollusc species and 91% of salamander species. The existing reserves provide conservation value for terrestrial molluscs and salamanders. This reserve network, however, should not be considered optimal for either taxa.     

How Well Will Brazil's System of Atlantic Forest Reserves Maintain Viable Bird Populations?

It is crucial for biodiversity conservation that protected areas are large and effective enough to support viable populations of their original species. We used a point count distance sampling method to estimate population sizes of a range of bird species in three Atlantic forest protected areas of size 5600, 22,500, and 46,050 ha. Population sizes were generally related to reserve area, although in the mid-sized reserve, there were many rare species reflecting a high degree of habitat heterogeneity. The proportions of forest species having estimated populations >500 ranged from 55% of 210 species in the largest reserve to just 25% of 140 species in the smallest reserve. All forest species in the largest reserves had expected populations >100, but in the small reserve, 28% (38 species) had populations <100 individuals. Atlantic forest endemics were no more or less likely to have small populations than widespread species. There are 79 reserves (>1000 ha) in the Atlantic forest lowlands. However, all but three reserves in the north of the region (Espírito Santo and states north) are smaller than 10,000 ha, and we predict serious levels of local extinction from these reserves. Habitat heterogeneity within reserves may promote species richness within them, but it may also be important in determining species loss over time by suppressing populations of individual species. We suggest that most reserves in the region are so small that homogeneity in the habitat/altitude within them is beneficial for maintenance of their (comparatively small) original species compliment. A lack of protection in the north, continued detrimental human activity inside reserves, and our poor knowledge of how well the reserve system protects individual taxa, are crucial considerations in biodiversity management in the region.     

自然保护区减缓和适应气候变化的管理有效性评估: 以广西12个典型自然保护区为例

建立自然保护区是生物多样性保护的根本措施, 而且自然保护区对减缓和适应气候变化具有重要的作用。生物多样性保护的压力在气候变化的胁迫下不断加剧, 因此, 有效的自然保护区管理必须考虑气候变化的影响。发展应对气候变化威胁的适应性管理技术以提高自然保护区管理有效性是自然保护区管理的迫切需求。但目前全球范围内还没有针对减缓和适应气候变化的自然保护区管理有效性评估工具。近半个世纪来广西气温持续升高且极端气候事件频次增加, 对广西各类生物生境产生了重要的影响。本文基于世界自然保护联盟(IUCN)的自然保护区减缓和适应气候变化管理框架和管理有效性评估框架, 在管理有效性跟踪工具(mangement effectiveness tracking tool, METT)基础上提出了自然保护区减缓和适应气候变化管理有效性评估工具(management effectiveness assessment tool of mitigation and adaptation on climate change, MEATMACC), 并使用该工具和METT对广西12个典型自然保护区进行了调查分析。结果表明: 国家级自然保护区的METT得分、MEATMACC得分分别比非国家级自然保护区高28.98%和43.91%; 国家级与非国家级自然保护区的METT得分无显著差异, 但MEATMACC得分差异极显著; 两个管理有效性评估工具得分率呈线性相关但差异不显著; 两个评估工具中背景、规划与影响3个要素得分率存在极显著差异。研究结果表明, 对于自然保护区减缓和适应气候变化的政策和技术支持仍需加强。     

Effectiveness of Nature Reserve System for Conserving Tropical Forests: A Statistical Evaluation of Hainan Island,China

Evaluating the effectiveness of existing nature reserve systems for the conservation of tropical forests is an urgent task to save the remaining biodiversity. Here, we tested the effectiveness of the reserve system on Hainan Island by conducting a three-way comparison of changes in forest area in locations within the reserves, adjacent to the reserves, and far outside of the reserves. We used a general linear model to control for the effects of covariates (historical forest area, elevation, slope, and distance to nearest roads), which may also be correlated with the changes in forest area, to better explain the effectiveness of the reserve system. From 2000 to 2010, the forest area inside Hainan’s nature reserve system showed an increase while adjacent unprotected areas and the wider, unprotected landscape both experienced deforestation. However, the simple inside-outside comparisons may overestimate the protective effect of the reserve system. Most nature reserves (>60%) showed increasing fragmentation. And the risk of rapid deforestation remained high at low elevations, where remaining forests tend to be easily logged and converted to commercial plantations. Future conservation efforts should pay more attention to those sites with less challenging environmental conditions.     

基于水鸟保护的长江流域湿地优先保护格局模拟

基于系统保护规划的理论和方法,以长江流域湿地为研究区,构建了基于气候、地貌分异的湿地生态地理综合分类单元,并将其作为宏观尺度湿地生态系统保护目标,同时考虑以湿地鸟类为代表的物种保目标,依托Marxan系统保护规划工具,确定了长江流域湿地保护具有不可替代性的优先保护格局。该格局能以最小的社会经济和土地资源代价最大程度的保护湿地生物多样性,对比现有湿地保护格局,最终确定了游离于现有保护体系外的湿地保护空缺。研究结果表明:长江流域源区和长江三角洲地区的湿地保护体系完善,无需新建保护区;金沙江流域湿地保护空缺主要分布在现有保护区周围,可以适当扩充保护区外围或调整边界;嘉陵江流域和长江上游干流流域的保护空缺严重,大面积集中在重庆西北部,乌江流域的贵州省习水县北部湖泊湿地存在保护空缺,这些区域建议适当新建保护区或者保护小区;长江中下游湿地保护空缺主要分布在湖北、湖南、江西与安徽境内的沿江湖泊湿地,建议建立湿地公园及合理进行河流岸坡修复。研究结果可为长江流域湿地保护体系调整、保护规划制定提供参考依据,从宏观层面上为长江流域湿地统筹保护及合理开发利用提供科学依据。     

青藏高原国家级自然保护区管理能力差异及其对保护成效的影响

青藏高原是我国重要的生态屏障。自然保护区能有效地保护生态安全和生物多样性, 评估自然保护区管理能力对保护成效的影响有利于自然保护区的科学保护与管理。本研究分析了青藏高原54处国家级自然保护区管理机构类型、资金、人员配置等管理能力方面的差异, 并利用归一化植被指数(normalized difference vegetation index, NDVI)研究不同自然保护区的保护成效, 揭示青藏高原国家级自然保护区管理能力与保护成效的关系, 为提升青藏高原自然保护区保护和管理成效提供依据。结果表明: (1)青藏高原国家级自然保护区管理机构行政级别差异较大, 包括厅局级(1处)、县处级(36处)、乡科级(16处)和股级(1处) 4个级别, 其中独立管理机构42处, 与其他机构合署办公的非独立管理机构12处, 行政级别和独立性影响保护成效, 行政级别较高、独立的管理机构的自然保护区保护成效较好。(2)青藏高原国家级自然保护区在单位管理资金、人均管理面积与巡护面积等方面与全国平均水平差异较大, 且专业人才普遍缺乏。建议重点关注青藏高原地区自然保护区保护管理的特殊性, 规范管理机构建设, 加强资金保障, 推动更多高水平专业人才从事保护工作, 进一步加大生态管护岗位设置与培训, 切实提高青藏高原地区自然保护区管理能力和保护成效。     

Threats and opportunities for freshwater conservation under future land use change scenarios in the United States

Freshwater ecosystems provide vital resources for humans and support high levels of biodiversity, yet are severely threatened throughout the world. The expansion of human land uses, such as urban and crop cover, typically degrades water quality and reduces freshwater biodiversity, thereby jeopardizing both biodiversity and ecosystem services. Identifying and mitigating future threats to freshwater ecosystems requires forecasting where land use changes are most likely. Our goal was to evaluate the potential consequences of future land use on freshwater ecosystems in the coterminous United States by comparing alternative scenarios of land use change (2001–2051) with current patterns of freshwater biodiversity and water quality risk. Using an econometric model, each of our land use scenarios projected greater changes in watersheds of the eastern half of the country, where freshwater ecosystems already experience higher stress from human activities. Future urban expansion emerged as a major threat in regions with high freshwater biodiversity (e.g., the Southeast) or severe water quality problems (e.g., the Midwest). Our scenarios reflecting environmentally oriented policies had some positive effects. Subsidizing afforestation for carbon sequestration reduced crop cover and increased natural vegetation in areas that are currently stressed by low water quality, while discouraging urban sprawl diminished urban expansion in areas of high biodiversity. On the other hand, we found that increases in crop commodity prices could lead to increased agricultural threats in areas of high freshwater biodiversity. Our analyses illustrate the potential for policy changes and market factors to influence future land use trends in certain regions of the country, with important consequences for freshwater ecosystems. Successful conservation of aquatic biodiversity and ecosystem services in the United States into the future will require attending to the potential threats and opportunities arising from policies and market changes affecting land use.