Water is a fundamental resource that is critical for the survival of all living things. Since pre-industrial times, climate change and other human activities have dramatically transformed the way that water is distributed globally. What patterns are beginning to emerge within nature as living things attempt to respond to these escalating changes and how would they most likely be affected if there were a shortage of water on Earth?
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In recent decades, climate change has often been linked to extreme weather events. Scientists have been using this term to describe the increased occurrence of temperature or precipitation conditions that are much higher or lower than average.
Contrasting changes in precipitation patterns are occurring in different global regions depending on complex meteorological factors. However, on average, the intensity of precipitation events and the variability of when they occur are both increasing. This means that many regions are less likely to receive a stable supply of rainfall and the intense precipitation that does occur is less likely to soak into the already saturated ground surface. Warmer temperatures contribute to faster evaporation of surface water, resulting in drought conditions that affect biodiversity, compromise soil fertility, and represent huge risks to human health.
Image 1: Map predicting global changes in precipitation intensity using a climate model
Since the 1960s, global water use by humans has more than doubled through its use for a wide range of sectors with agriculture being by far the largest user of freshwater. Domestic water withdrawals have shown over a 600% increase since the 1960s to supply the life of the growing global population and the wide range of modern household technologies people use nowadays in their day-to-day life.
Image 2: Water withdrawals for different sectors, 1960-2014
How Would Living Things Most Likely Be Affected If There Were A Shortage of Water on Earth?
Water is essential for the metabolic reactions needed to keep living things alive as well as supporting the majority of species in many other indirect ways. The high specific heat capacity of water creates stable conditions for species to reproduce and regulate their body temperature.
Decline in Aquatic Ecosystems
The relationship between water depth and temperature is also critical for many organisms because, as water bodies dry and become shallow, the average temperature of the water and therefore the habitat, will generally increase. Thus, declines and geographical shifts in aquatic ecosystems will inevitably lead to the extinction of many species that have a low tolerance to water level and temperature changes and that are unable to migrate or adapt quickly enough to the new environment.
The increased variability and intensity of precipitation as a result of climate change forces humans to build more dams with larger storage capacities in order to meet rapidly growing water consumption demands. These reduce the flow rate of river systems and lead to a loss of environmental flows which are crucial to maintaining riverine ecosystems.
The drying of water means fewer rivers will reach the sea and those that do will be more likely to be ephemeral rather than flowing all year round. This results in the depletion of estuarine and wetland ecosystems, which are both known to support large amounts of unique plant and animal species and are particularly important for providing nurseries for fish, amphibians, and other types of species. Both estuaries and wetlands support large amounts of life that would not be able to survive in drier conditions and contain comparable levels of productivity to tropical forests.
Habitat Destruction and Increased Diseases
A lack of constant rainfall due to climate change can cause a change in habitat distributions globally and this can force animals to emigrate to find a new area of suitable habitat. For example, a species called the Northern Dusky Salamander found in the US was found to be twice as likely to emigrate during drought conditions.
Several studies have also shown that drought conditions have been linked to an increased abundance of parasites and diseases in water sources. Drier conditions result in fewer and smaller water bodies, meaning many animals will drink from the same water source leading to the rapid spread of diseases. More animals will also be suffering from dehydration, which weakens their immune systems and further encourages the spread of disease.
Wildfires
In many global regions, extended dry periods brought about by climate change can increase the likelihood of runaway wildfires which have the capability of killing millions of organisms. A recent example of this was seen during the 2020 Australian bushfires, which were brought about by the hot and dry conditions. These were made 30% more likely by climate change and resulted in the death of 143 million mammals along with almost three billion other vertebrate animals.
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Soil Erosion
Erosion of topsoil and the loss of soil quality that can occur from prolonged dry periods reduces the diversity of soil fauna and lowers the rate of nutrient cycling. This limits plant diversity as plants that are not adapted to live in low soil fertility cannot survive and become locally extinct. As a result, this can create a cascade effect where the extinction of one species leads to population imbalances of other local species and can ultimately contribute to ecosystem collapse and large-scale loss of diversity.
Effects on Humans and Societies
Human societies also have a strong reliance on water as it is one of the commodities required not only for basic survival but also to hold together complex modern-day economic systems that can raise standards of living and allow people to prosper. However, due to climate change, the overuse of groundwater aquifers, and the growth in the global population (particularly of the middle class), freshwater reserves are now becoming scarce in many regions for humans, too.
Saudi Arabia is an example of a country that could struggle in the future. The nation has used up almost its entire groundwater supplies and its lack of surface water reserves means it could run out of water entirely by 2029. One of the main reasons for Saudi Arabia’s high-water use is due to crop irrigation. This is also the key reason in many other locations such as the drying of the Aral Sea. This was once the fourth-biggest lake in the world and is now about 10% of its original size. The diminishing lake size resulted in salt pollution and food shortages for the nearby communities and has led to the infant mortality rate around twice as high as in nearby regions.
A scarcity of water can also act as a catalyst for conflict. An example of this was seen in the fighting in the Darfur region of Sudan which started in 2003 and was linked to a disagreement over the ownership of a diminishing water supply and the conflict resulted in the death of around 400,000 Africans.
Agriculture
The loss of wetlands through climate change could also be a problem for the cultivation of rice, which requires waterlogged conditions and forms a staple part of the diet of over half of the global population. Changes like these to the production of globally significant crops could cause food prices to skyrocket resulting in millions of people moving back down below the poverty line and facing malnutrition and starvation.
Conclusion
So, how would living things most likely be affected if there were a shortage of water on Earth? Well, it is clear that there would be countless negative consequences for the natural world. These would also act as further fuel to the numerous other human factors driving the ecological crisis. Humans are developing an addiction to high water usage through indirect activities that feed the economic systems, meaning that water scarcity creates a large threat to national security and can spark conflict.
Whilst humans can attempt to partially adapt to the problem of a dwindling freshwater supply by using technology such as desalination plants, other species cannot. This means it is essential that global action is taken to limit climate change and to impose tighter regulations to support the sustainable use of freshwater reserves.
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