Emerging threats and persistent conservation challenges for freshwater biodiversity
- Authors: Reid, Andrea , Carlson, Andrew , Creed, Irena , Eliason, Erika , Gell, Peter , Johnson, Pieter , Kidd, Karen , MacCormack, Tyson , Olden, Julian , Ormerod, Steve , Smol, John , Taylor, William , Tockner, Klement , Vermaire, Jesse , Dudgeon, David , Cooke, Steven
- Date: 2019
- Type: Text , Journal article
- Relation: Biological Reviews Vol. 94, no. 3 (2019), p. 849-873
- Full Text: false
- Reviewed:
- Description: 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.
Size and quantity of woody debris affects fish assemblages in a sediment-disturbed lowland river
- Authors: Howson, Travis , Robson, Belinda , Matthews, Ty , Mitchell, Bradley
- Date: 2012
- Type: Text , Journal article
- Relation: Ecological Engineering Vol. 40, no. (2012), p. 144-152
- Full Text: false
- Reviewed:
- Description: Responses by fish assemblages to individual restoration actions among a suite of channel modifications are not well understood. We investigated whether increasing woody debris abundance, without significant change to channel morphology, would increase native fish abundance and species richness in a sediment-disturbed river channel (Glenelg River, Victoria, Australia). We conducted a Before-After, Control-Impact design experiment at twelve locations containing either a high (n=6) or low (n=6) quantity of large woody debris (LWD). We added small woody debris (SWD) to half (n=6: 3 high, 3 low LWD densities) of the locations to increase woody debris complexity without the impacts on channel morphology associated with LWD manipulations. Fish species richness and abundance was quantified using electrofishing surveys before (4 sampling trips) and after (3 sampling trips) SWD addition. Fish species richness was not associated with high or low quantities of LWD or with types of woody debris (LWD or SWD). Addition of SWD altered fish assemblage composition but the effect depended on LWD quantity. SWD additions to locations with low LWD quantities increased abundance of two, wood-affiliated species: Philypnodon grandiceps and Gadopsis marmoratus. SWD additions to locations with high LWD quantities increased abundance of P. grandiceps and Galaxias olidus. Fish body size was important in detecting a response to added SWD because for two species, only certain size classes responded: adults of P. grandiceps (>50. mm TL) and juveniles of G. marmoratus (<123. mm TL). Fish assemblages responded positively to increased density of SWD through local increases in abundance, despite channel sedimentation. Unlike LWD, SWD is relatively cheap to place in rivers because it does not require heavy machinery and can be obtained without tree mortality. The use of SWD to assist in habitat restoration, especially for small species of native fish and juvenile fish, should be considered as a strategy in river restoration. © 2012.