Freshwater ecosystems are a crucial part of the world's climate; they provide a habitat for a wide variety of plants and animals, boosting biodiversity and maintaining a healthy ecosystem. The biodiversity of freshwater ecosystems is thought to be in a state of crisis, however. The world puts a lot of demands on our freshwater resources, which are used by industries such as agriculture, energy production, mining, transportation, and tourism, for example. These ecosystems have been under serious threat for a long time, even while scientists and activists have tried to draw attention to the problem. There are a number of threats to freshwater habitats, including climate change, pollution, overuse, invasive species, and habitat degradation or loss.
A new study reported in Nature has suggested that freshwater habitats in Europe have reversed recent gains, and recovery of biodiversity in these areas has stopped. Until the 2010s, there were notable gains in markers of biodiversity such as the diversity of species, functional richness, and abundance. After the 2010s, those gains slowed down significantly.
The study showed that in freshwater communities that are downstream of urban areas, croplands, and hydrological alterations like dams, there were disturbing patterns emerging. When urban areas or cropland were present, biodiversity was generally lower. Cropland tended to weed out species, leaving only those that were tolerant to the runoff produced by agriculture. Sensitive and rare species were found to be in serious decline near urban areas. When dams were present, there were fewer species and less functional diversity. Dams also change the character of freshwater ecosystems by increasing sediment levels, changing flows, and altering temperatures. The loss of rare species near dams was pronounced, while there were also significant declines in the dominant species.
The prospects for recovery are also not good. The study authors suggested that efforts at improving water quality and restoring habitats had a positive impact that could be observed in freshwater communities in the 1990s and 2000s. However, the effectiveness of those measures appears to be diminishing.
While legislation helped reduce pollution and acidification in freshwaters, starting around 1980, the pressures and threats to these areas have only increased, and more needs to be done to protect these environments, the work suggested. The study authors are calling for intensified and renewed strategies and efforts to boost recovery in freshwater ecosystems.
A new report has also noted that freshwater ecosystems are emitting significant amounts of methane, which is a powerful greenhouse gas. This only reinforces the notion that it is time to help our freshwater communities recover once more.
"Our findings raise a critical alarm for the health of European freshwater ecosystems. The slowdown in recovery rates demands a comprehensive reevaluation of existing mitigation measures and the implementation of new, adaptive strategies. Time is of the essence, and we must act swiftly to protect these essential ecosystems," noted study co-author Dr. Gábor Várbíró from the Centre for Ecological Research.