Emerging threats and persistent conservation challenges for freshwater biodiversity

Abstract

In the 12 years since Dudgeon et al. (2006) reviewed major pressures on freshwater ecosystems, the biodiversity crisis in the world's lakes, reservoirs, rivers, streams and wetlands has deepened. While lakes, reservoirs and rivers cover only 2.3% of the Earth's surface, these ecosystems host at least 9.5% of the Earth's described animal species. Furthermore, using the World Wide Fund for Nature's Living Planet Index, freshwater population declines (83% between 1970 and 2014) continue to outpace contemporaneous declines in marine or terrestrial systems. The Anthropocene has brought multiple new and varied threats that disproportionately impact freshwater systems. We document 12 emerging threats to freshwater biodiversity that are either entirely new since 2006 or have since intensified: (i) changing climates; (ii) e-commerce and invasions; (iii) infectious diseases; (iv) harmful algal blooms; (v) expanding hydropower; (vi) emerging contaminants; (vii) engineered nanomaterials; (viii) microplastic pollution; (ix) light and noise; (x) freshwater salinisation; (xi) declining calcium; and (xii) cumulative stressors. Effects are evidenced for amphibians, fishes, invertebrates, microbes, plants, turtles and waterbirds, with potential for ecosystem-level changes through bottom-up and top-down processes. In our highly uncertain future, the net effects of these threats raise serious concerns for freshwater ecosystems. However, we also highlight opportunities for conservation gains as a result of novel management tools (e.g. environmental flows, environmental DNA) and specific conservation-oriented actions (e.g. dam removal, habitat protection policies, managed relocation of species) that have been met with varying levels of success. Moving forward, we advocate hybrid approaches that manage fresh waters as crucial ecosystems for human life support as well as essential hotspots of biodiversity and ecological function. Efforts to reverse global trends in freshwater degradation now depend on bridging an immense gap between the aspirations of conservation biologists and the accelerating rate of species endangerment.

No biotic homogenisation across decades but consistent effects of landscape position and pH on macrophyte communities in boreal lakes

“…We also aimed to discover if these patterns differ between species-, phylogenyand trait-based beta diversity (i.e. In addition, freshwater ecosystems are globally considered biodiversity hotspots and provide valuable ecosystem goods and services to humans, but are intensively threatened by global change (Dudgeon et al 2006, Vörösmarty et al 2010, Vilmi et al 2016, Reid et al 2018). We used presence-absence data of aquatic macrophytes from five different decades from small boreal lakes and used generalised dissimilarity modelling to study separately the relationship between different biodiversity facets and environmental gradients among five different time periods.…”

Dynamic contributions of intermittent and perennial streams to fish beta diversity in dryland rivers

“…Freshwater ecosystems are spotlighted in the current biodiversity crisis (Harrison et al, ), where biotas continue to experience dramatic changes in composition and loss of endemism (Reid et al, ). The discrete boundaries and dendritic topology of rivers contribute to the immense diversity of freshwater organisms, including fish, but also make them highly sensitive to multiple interacting threats (Altermatt, ; Craig et al, ; Olden et al, ).…”

Searching for responsible and sustainable recreational fisheries in the Anthropocene

“…Recreational fisheries operate in diverse aquatic ecosystems around the globe; from the ice‐covered freshwater lakes of northern Finland to the coastal flats habitats of the Seychelles, from the depths of the Amazon Basin to the Great Barrier Reef. The motivations for participation in recreational fishing are diverse (Fedler & Ditton, ), but what unites all recreational fishers is that it is a leisure activity ( i.e ., it is conducted largely “for fun”; Pitcher & Hollingworth, ) that also contributes to personal nutrition (Cooke et al ., ) in some instances ( i.e ., when fish are not released). Recreational fishing is also big business, creating thousands of jobs across the world.…”

“…The many ecosystem services that can be derived from fish populations (Lynch et al ., ) require that recreational fisheries be conducted in a manner that is sustainable. Yet, recreational fisheries do not operate in a vacuum and the fish and fish habitat upon which recreational fisheries are based, are in part very strongly and pervasively influenced by a range of non‐fishing related anthropogenic disturbances, such as water abstraction, hydropower, climate change, invasive species and pollution (Costello et al ., ; Dudgeon et al ., ; Reid et al ., ), as well as other fisheries sectors. Thus, sustainable recreational fisheries depend on also addressing threats external to recreational fisheries and if these threats cannot be ameliorated easily (largely due to socio‐political or economic constraints; Cowx et al ., ), recreational fisheries must be managed within a constraint productivity space to operate safely (Carpenter et al ., ).…”