Climate change and consequences
Rising temperatures over time are changing weather patterns and upsetting the normal balance of nature. This poses many risks to human beings and all other forms of life on Earth.
The climate crisis has increased the average global temperature and is leading to more frequent temperature extremes, such as heat waves and increased water evaporation, which, together with the lack of rainfall, increases the risk of severe droughts.
More frequent droughts and higher water temperatures will cause a decline in water quality by encouraging the growth of algae and toxic bacteria, which will exacerbate the problem of water scarcity.
Severe thunderstorms will become more common and intense due to higher temperatures, with flash floods expected to become more frequent.
Rising sea levels will reduce the amount of fresh water available, as seawater will further penetrate aquifers. This could also lead to greater saltwater intrusion into freshwater bodies, affecting agriculture and drinking water supplies.
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Consequences for aquatic ecosystems
It is no secret that climate change has a serious impact on the quality and ecology of aquatic environments. Researchers at Eawag have revealed that human responses to climate change have an equally strong impact on our water systems, for example in the agriculture and hydropower sectors.
When thermometers in California recorded scorching temperatures in the summer of 2000, the salmon in the Klamath River were also affected. The water temperature caused them to congregate in unusually large numbers in confined spaces, creating the perfect food source for pathogens. At the same time, farmers redirected increasing amounts of water to their dry fields, reducing the flow of the river. The result was the death of 70,000 fish. It later emerged that this devastating salmon slaughter could have been avoided if farmers had not diverted so much water to irrigate their land.
In a recently published study, Eawag researchers clearly demonstrated that climate change is not the only cause of these devastating effects on aquatic ecosystems. Based on an extensive literature search and interviews with experts, the researchers concluded that how humans respond to climate change is equally crucial, as exemplified in the case of California: by intensifying crop irrigation or switching to more drought-resistant varieties.
The indirect effects of climate change are often underestimated
We have long been aware of the direct impact of climate change on natural freshwater systems. For example, the temperature of freshwater environments in mountainous regions increases disproportionately. But the flow and drainage times of watercourses are also changing, due to increased summer droughts and the ongoing melting of glaciers. This not only threatens the habitats of aquatic life and their biodiversity. Some 1.5 billion people who depend on water resources in these mountainous regions will also suffer if the quality and quantity of drinking water deteriorate.
On the other hand, the impacts of these indirect measures, i.e. the human response to climate change, are little studied in comparison. In the context of the ‘Hydro-CH2018’ hydrological scenarios of the National Centre for Climate Services NCCS, Eawag researchers, under the leadership of Christian Stamm (Eawag group leader) and Florian Altermatt (Eawag group leader and associate professor at the University of Zurich), compared direct and indirect impacts on the quality and ecology of water bodies. They found that the indirect impacts of climate change may not only increase the direct impacts, but even exceed them in the short term.
One of the main factors, besides agriculture, is hydropower. Switzerland, which strives to become climate neutral by 2050, is pushing ahead with the transition to renewable energies, which includes the expansion of hydropower. But good measures to combat greenhouse gases often have a negative impact on water systems. Here is what Morgane Brosse, evolutionary biologist and first author of the Eawag research paper, has to say: ‘When less water flows downstream of hydropower plants, the river heats up and there is a risk that its bed will dry up in places. Dams or hydropower plants along rivers often form barriers that hinder the migration of aquatic organisms’. According to the researcher, this in turn creates favourable conditions for disease and reduces genetic diversity, both of which are already an unpleasant direct consequence of climate change.
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Tackling climate change and biodiversity loss together
So is it better to stop taking measures against climate change in the future or what conclusions could the authors draw from this study? Brosse: ‘It is undeniable that we must act urgently to stop climate change and reduce its direct impact on all ecosystems. But we must carefully consider the consequences of our actions to avoid making the situation worse. For the agricultural sector this means, for example, evaluating new crops not only in terms of their climatic niche and cultivability, but also in relation to their water requirements and the footprint of fertilisers or pesticides on aquatic systems. In particular, according to Brosse, this involves offering incentives to agriculture to ensure that new practices do not have an even more damaging impact on aquatic systems.
And what about hydropower? Brosse replies: ‘Promoting sustainable energy resources is of paramount importance. However, it is becoming increasingly evident that hydropower, although renewable, is not sustainable in many cases. When every drop of water is used, biodiversity suffers the most. However, if it were possible to optimise the use of reservoirs so that stored water is not only used to generate electricity but also to overcome droughts, this would be a win-win solution for both climate protection and biodiversity.”
Warming seas, changing marine biodiversity
The seas are warming even in depth and rising temperatures are causing drastic changes in marine biodiversity, from the disappearance of the most sensitive species characteristic of our seas to the invasion of others, often alien, that are better adapted to an increasingly warmer sea. Climate change poses a serious threat to marine life, including coral reefs and fisheries, with repercussions for marine ecosystems, economies and societies, particularly those most dependent on natural resources.
As the oceans warm, the circulation of the seas changes, evaporation regimes change and, with them, precipitation on land.
As the climate changes, plants, insects and animals take to the mountaineering
As the planet warms up, species and vegetation shift. In the Alps, plants, insects, birds and trees adapt and migrate to higher altitudes.
The most tangible sign of the warming of the Alps is probably the retreating glaciers and rising temperatures that lead to earlier melting of snow in the mountains and earlier vegetation, as well as warmer spring days that can disturb the balance of flora and fauna.
Climate change also affects health
The heavy heat of recent years has had an impact on the increase in cardiovascular diseases and the spread of infectious diseases, in particular two diseases, largely transmitted by mosquitoes and ticks, such as dengue fever and malaria. Cases of leishmaniasis and Lyme disease were also reported as increasing.
The incidence of allergies and asthma is also increasing as rising temperatures are leading to changes even in the flowering of plants and the spread of pollen, with negative effects both for those sensitive to these allergens and asthmatics.