A new global map of threats to freshwater wildlife could help conservation planners identify where different pressures are doing the most harm, with Canadian species facing risks ranging from dams and fishing to pollution and invasive species.

The research, published in the journal Science, examined known threats to more than 2,100 freshwater species on the International Union for Conservation of Nature’s red list, according to reporting by CBC’s Bryce Hoye. The IUCN estimates that a quarter of freshwater species are at risk of extinction.

Researchers mapped threats affecting amphibians, reptiles, fish, mammals, and dragonflies and damselflies. They produced a colour-coded map showing regional threat intensity, alongside an index connecting particular pressures to species declines.

Christophe Brabant, a McGill University PhD candidate involved in the research, told CBC the method accounts for the different ways species respond to threats rather than assuming they are all affected equally.

Agriculture and aquaculture ranked as the leading threat globally, particularly in the global south. Pollution came second, with especially strong impacts in eastern China, India and Europe. Biological resource use, including hunting and fishing, ranked third.

In Canada, major threats included dams and water diversions, hunting and fishing, agriculture, development, pollution, energy production and mining. The map also identified a band of disease and invasive-species pressures across several provinces near the Canada–U.S. border.

The findings point to the need for conservation measures tailored to particular places and species, rather than a single approach everywhere, Brabant said.

The researchers also cautioned against interpreting climate change’s limited prominence on the map as evidence that it poses little danger. Brabant said climate threats are not recorded well in the red-list information used by the study.

Separate long-term monitoring at the Experimental Lakes Area in northwestern Ontario illustrates that concern. Research described by CBC found that local air temperatures rose about 2 C between 1986 and 2016, while lake ice coverage shortened by nearly three weeks. Adult lake trout also became smaller during that period.

The map does not settle how conservation money should be spent. University of British Columbia environmental economist Frederik Noack told CBC that funding decisions must also weigh factors beyond threat intensity, including the likelihood that conservation efforts will succeed.

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