Restoring streams in an urbanizing world

1. The world's population is increasingly urban, and streams and rivers, as the low lying points of the landscape, are especially sensitive to and profoundly impacted by the changes associated with urbanization and suburbanization of catchments. 2. River restoration is an increasingly popular management strategy for improving the physical and ecological conditions of degraded urban streams. In urban catchments, management activities as diverse as stormwater management, bank stabilisation, channel reconfiguration and riparian replanting may be described as river restoration projects. 3. Restoration in urban streams is both more expensive and more difficult than restoration in less densely populated catchments. High property values and finely subdivided land and dense human infrastructure (e.g. roads, sewer lines) limit the spatial extent of urban river restoration options, while stormwaters and the associated sediment and pollutant loads may limit the potential for restoration projects to reverse degradation. 4. To be effective, urban stream restoration efforts must be integrated within broader catchment management strategies. A key scientific and management challenge is to establish criteria for determining when the design options for urban river restoration are so constrained that a return towards reference or pre‐urbanization conditions is not realistic or feasible and when river restoration presents a viable and effective strategy for improving the ecological condition of these degraded ecosystems.     

重建沿海韧性——旧金山湾盐沼修复及其启示

潮洪灾害、海平面上升已促使沿海城市由“抵御”向“适应”转变。通过修复盐沼提高海岸防护的韧性,已被认可是一种有效的适应对策。选取旧金山湾为案例,基于文献和实地调研,探究城市盐沼修复的实践路径和设计方法。研究表明,适应性管理是旧金山湾三代修复实践得以不断优化、发展的关键,帮助制定、调整目标和方法,弹性应对不确定性;旧金山湾通过发展修复设计导则,加速盐沼修复,促进形成更自然的盐沼;并修复过渡区,提供盐沼向内陆迁移的空间,缓解海岸挤迫。最后,提出中国河口海岸城市实施盐沼修复的可借鉴之处,推进海岸防护措施向基于自然的途径转变。     

Synchronous Waves of Failed Soft Sweeps in the Laboratory: Remarkably Rampant Clonal Interference of Alleles at a Single Locus

It has increasingly been recognized that adapting populations of microbes contain not one, but many lineages continually arising and competing at once. This process, termed “clonal interference,” alters the rate and dynamics of adaptation and biases winning mutations toward those with the largest selective effect. Here we uncovered a dramatic example of clonal interference between multiple similar mutations occurring at the same locus within replicate populations of Methylobacterium extorquens AM1. Because these mutational events involved the transposition of an insertion sequence into a narrow window of a single gene, they were both readily detectable at low frequencies and could be distinguished due to differences in insertion sites. This allowed us to detect up to 17 beneficial alleles of this type coexisting in a single population. Despite conferring a large selective benefit, the majority of these alleles rose and then fell in frequency due to other lineages emerging that were more fit. By comparing allele-frequency dynamics to the trajectories of fitness gains by these populations, we estimated the fitness values of the genotypes that contained these mutations. Collectively across all populations, these alleles arose upon backgrounds with a wide range of fitness values. Within any single population, however, multiple alleles tended to rise and fall synchronously during a single wave of multiple genotypes with nearly identical fitness values. These results suggest that alleles of large benefit arose repeatedly in failed “soft sweeps” during narrow windows of adaptation due to the combined effects of epistasis and clonal interference.     

Limited potential for adaptation to climate change in a broadly distributed marine crustacean

The extent to which acclimation and genetic adaptation might buffer natural populations against climate change is largely unknown. Most models predicting biological responses to environmental change assume that species' climatic envelopes are homogeneous both in space and time. Although recent discussions have questioned this assumption, few empirical studies have characterized intraspecific patterns of genetic variation in traits directly related to environmental tolerance limits. We test the extent of such variation in the broadly distributed tidepool copepod Tigriopus californicus using laboratory rearing and selection experiments to quantify thermal tolerance and scope for adaptation in eight populations spanning more than 17° of latitude. Tigriopus californicus exhibit striking local adaptation to temperature, with less than 1 per cent of the total quantitative variance for thermal tolerance partitioned within populations. Moreover, heat-tolerant phenotypes observed in low-latitude populations cannot be achieved in high-latitude populations, either through acclimation or 10 generations of strong selection. Finally, in four populations there was no increase in thermal tolerance between generations 5 and 10 of selection, suggesting that standing variation had already been depleted. Thus, plasticity and adaptation appear to have limited capacity to buffer these isolated populations against further increases in temperature. Our results suggest that models assuming a uniform climatic envelope may greatly underestimate extinction risk in species with strong local adaptation.     

Preparing Wildlife for Climate Change: How Far Have We Come?

Global biodiversity is in unprecedented decline and on-the-ground solutions are imperative for conservation. Although there is a large volume of evidence related to climate change effects on wildlife, research on climate adaptation strategies is lagging. To assess the current state of knowledge in climate adaptation, we conducted a comprehensive literature review and evaluated 1,346 peer-reviewed publications for management recommendations designed to address the consequences of climate change on wildlife populations. From 509 publications, we identified 2,306 recommendations and employed both qualitative and quantitative methods for data analysis. Although we found an increase in the volume and diversity of recommendations since 2007, a focus on protected areas (26%, 596 of 2,306 recommendations) and the non-reserve matrix (12%, 276 of 2,306 recommendations) remained prominent in the climate adaptation literature. Common concepts include protected areas, invasive species, ecosystem services, adaptive management, stepping stones, assisted migration, and conservation easements. In contrast, only 1% of recommendations focused on reproduction (n = 26), survival (n = 14), disease (n = 26), or human-wildlife conflict (n = 24). Few recommendations reflected the potential for local-scale management interventions. We demonstrate limited advancement in preparing natural resource managers in climate adaptation at local, management-relevant scales. Additional research is needed to identify and evaluate climate adaptation strategies aimed at reducing the vulnerability of wildlife to contemporary climate change. © 2020 The Wildlife Society.     

Hydrologic restoration of coastal wetlands

Hydrologic modification of coastal wetlands is pervasive, continuing and longstanding in the US. Appreciation for the subtleties of the direct and indirect effects of hydrologic changes on emergent vegetation, soils and co-dependent flora and fauna is contributing to restoration efforts. However the results of wetland restoration/rehabilitation are moslty empirical, rather than scientific in understanding. Science is contributing to the management interest by providing documentation of the past and present failures and successes, and, unveiling the fundamental understanding necessary to move from one wetland to another in an informed and adaptable manner. The papers in this volume are introduced within this framework.     

气候变化条件下全氟化合物对海岸带可持续发展的影响及管控策略

海岸带生态系统为人类提供了食物、水等丰富的物质以及文化、休闲等生态系统服务。但由于全氟化合物等污染物的排放和气候变化的影响,海岸带地区环境日益恶化、资源枯竭、极端气候灾害加剧。这些问题直接导致了海岸带水质下降、近海生物多样性减少、生物群落结构变化,海岸带生态系统可持续发展受到影响。全氟化合物在自然环境中难以降解,会沿食物链在生物体内累积和放大进而对人类健康造成风险。随着氟化工产业在我国的快速发展、新型全氟化合物的不断更替以及气候变化的加剧,全氟化合物对海岸带生态的影响面临着极大的不确定性。为了更好地服务海岸带生态系统的可持续发展,目前仍需要加快完善立法保障,在全国范围内对全氟化合物进行监测;将海洋与陆地作为一个有机整体,统筹陆地影响和海岸带管控,严格控制污染物的排放。