On the 2nd February World Wetlands Day is celebrated, commemorating the date of the adoption of the Convention on Wetlands on 2nd February 1971 in Ramsar, Iran. The purpose of World Wetlands Day is to have an annual date of global advocacy and events designed to raise awareness about the ecological value of wetlands for humanity and the planet, and to promote the ‘sustainable use’ of wetland habitats. The theme of World Wetlands Day 2019 is ‘Wetlands and Climate Change’, with the stated aim to initiate action against the drainage of wetlands.
Wetlands are recognised as playing an invaluable role in mitigating against the impacts of climate change, being described as a ‘natural solution’. Wetlands capture and store carbon to reduce atmospheric greenhouse gases. They also provide resilience against extreme weather events by absorbing and storing excess rainfall, thereby preventing flooding. During dry seasons, wetlands also release stored water therefore preventing drought events and alleviating water shortages.
As the incidence of extreme weather events associated with climate change continues to increase at an exponential rate, wetlands play a pivotal ecological role. However, wetlands are also being drained at an increasing rate, to meet the demands of economic development and the needs of a growing global population. Thus, with ever-smaller areas of wetlands, existing wetlands are put under greater strain and feel the pernicious effects of climate change, such as temperature variations, rainfall variability, and sea level rise.
Moreover, a significant degree of focus has been on the impact that declining wetland habitats has upon humans and their livelihoods. It is also imperative to consider the non-human inhabitants of wetlands that are also negatively impacted by the declining resilience of wetland areas, and other effects of climate change.
Danube wetlands, climate change, and sturgeon
Rivers and their floodplains are perhaps the most common wetland environments. In Europe, the Danube river basin is home to 81 million people and provides important ecosystem services ranging from drinking water, flood protection, income and recreation opportunities. However, over the last century the floodplain area of the Danube has reduced by more than 80%.
Wetlands in the Danube River basin are also highly valuable habitats for rare and endangered species, including the Danube’s ‘flagship species’ – sturgeon. Sturgeon are recognised as the planet’s most critically endangered group of species; and climate change has emerged as another threat to their existence, alongside poaching and overfishing, habitat fragmentation, and habitat degradation.
Sturgeon are said to be an indicator of the health of rivers and aquatic environments. Continuing declines of sturgeon populations in the Danube suggest that the river and delta system is not at optimal conditions for sturgeon population to flourish.
Sturgeon are highly sensitive to changes in environmental conditions, and the fish populations take a long time to recover from decline caused by the pressures from both humans and the environment. Climate change is exacerbating the pressure upon sturgeon populations. Changing weather and rises in the average of global temperatures can have drastic impacts upon fragile ecosystems. Increased temperatures in rivers and aquatic systems can limit the availability of food and decrease the availability of suitable spawning habitats for sturgeon. If the temperature of the water increases too much sturgeon may struggle to spawn. In the event that sturgeon do manage to find a suitable spawning location, lower concentrations of oxygen in the water might cause problems for sturgeon at younger life stages, as they require higher oxygen concentrations than older fish in order to survive.
Thus, climate change poses significant challenges to an already imperiled species. A key message delivered by Dr Harald Rosenthal at the 8th International Sturgeon Symposium in Vienna in 2017, was that there is a desperate need to integrate the change caused by climate change into longer term plans for sturgeon conservation. Climate change will significantly alter the wetland habitats, rivers, and oceans that sturgeon inhabit, but these “fish have no green card, no passport, or ticket” – they can’t relocate to a more amenable habitat. Read my blog, ‘Sturgeon: Unlikely geopolitical subjects’ written following the symposium for my reflections on the event.
Instead there is a need to ensure that wetland environments are restored and conserved. They should be sustainably used rather than drained or utilised for building projects. Protecting wetland environments can help humans to deal with the onslaught of climate change, and can also help to protect critically endangered species such as the sturgeon in the Danube.