Water - land - soil
Availability of water
Viewed from space, the earth appears as a blue planet—about 71 per cent of its surface is covered with oceans. The water of this earth is constantly moving: The global water cycle, driven by the processes of evaporation, precipitation and surface runoff describes the exchanges between the oceans, the mainland and the atmosphere. At the same time, only a small portion can be used as drinking water—according to estimates, the portion of freshwater is 2.5 to 3.5 per cent. Just under 69 per cent of that is stored in glaciers and the icecaps, about 30 per cent in groundwater. A mere 0.3 per cent of global freshwater is in surface bodies of water, that is, in lakes, rivers and swamps. The global distribution of freshwater is inherently unequal. We can differentiate roughly between humid (damp) areas and arid (dry) areas. In humid areas (66% of the surface of the mainland), precipitation is higher than evaporation, in arid areas (34% of the surface of the mainland) it is the other way round.
Humans have always influenced the water cycle by removing water, sealing land or damming rivers. Against the backdrop of industrialization and the rapidly growing world population, the global consumption of clean drinking water has risen sharply, particularly in the last few decades. In some regions of the world, this overuse leads to “water stress”, namely when the removal of “blue water” exceeds a certain percentage of the entire resource. Blue water includes rivers, lakes, groundwater, ice and glaciers. The main causes of water stress are agriculture, industry and private households, whereby the first of these uses by far the most, namely 70 per cent. According to the Food and Agriculture Organization of the United Nations (FAO), agriculture’s portion of total water consumption has tripled in the last 50 years. In the future, it is assumed that it will rise by another approx. 20 per cent. Intensive irrigation of fields, especially in dry areas, leads to environmental problems as this is often done at the cost of other ecosystems, which are threatened with degradation or desiccation as a result.
In addition to a quantitative lack of water, the pollution and poisoning of bodies of water present a momentous problem. Through waste water from industry and private households as well as the excessive use of fertilizers in agriculture, heavy metals, pesticides and nitrates, among others, get into the water. While bodies of water in early-industrialized countries were able to recover slowly, pollution today is steadily increasing, particularly in densely populated regions in emerging countries.
Based on World Health Organization estimates, 748 million people worldwide had no access to clean drinking water in 2012, of whom 90 per cent lived in Sub-Saharan Africa and Asia. One of the consequences of polluted drinking water is diarrhoea, an illness that kills an estimated 500,000 people every year.
Global trends in land-use change
One of the key environmental observations of the past few decades is the expansion of agricultural and residential areas at the cost of natural land cover. This so-called land-use change can be interpreted as a direct consequence of the rapidly growing world population. It indeed manifests itself very differently from region to region; however some general global trends can be recorded, such as the expansion of the area used for agriculture already mentioned, the substantial increase of pastures as well as the reduction of forests and wetlands.
The destruction of forests has been happening since antiquity; wood has always, after all, been a building material and source of fuel. According to FAO figures, the global forest area, however, has been reduced by 120 million hectares in the last 25 years, which is equivalent to an area approx. 3.5 times the size of Germany. While measures such as reforestation and sustainable forest management have led to deforestation decreasing and wooded areas increasing in many countries, nonetheless from a global point of view, the extensive forest clearance in the tropics, in Canada or Argentina mean that overall the balance is negative.
In many respects, logging in tropical rainforests has various serious consequences: On the one hand, the tropical forests boast far and away the greatest biodiversity on earth, so that the destruction and increased dissection of habitats lead to the irreversible loss of many species. On the other hand, the rainforest plays an important role, from a global point of view, in regulating climate, as the most significant CO2-sink on earth. In countries such as Brazil, Malaysia and Indonesia, rainforest clearances cause an increasing proportion of CO2 emissions as part of total emissions, which not only has an effect locally but also globally.
By now it is not only the timber industry or traditional shifting cultivation which cause deforestation. In the global economy, branched out all over the world, land as a resource has become a sought-after object of the finance industry, as planting agricultural commodities such as grains, oil palms, soya or cotton can earn a lot of money. This has recently led to both state actors and corporations from the United States, western Europe, Saudi Arabia but also China and Japan, leasing or acquiring large tracts of land in primarily less well-developed countries. This profit-oriented land grabbing now affects between 10 and 30 per cent of the global arable land, according to World Bank estimates.
But it is not only the increasing hunger for agricultural commodities that is destroying forest areas. In recent years, the production of iron ore, cobalt, coal and aluminium has increased dramatically, and in China alone, the mining sector grew by one-third from 2005 to 2010. Large mines are often formed in sensitive regions that have so far been untouched, for example, the Brazilian bauxite mine at Rio Trombetas, which destroys 300 hectares of rainforest every year. Such mining activities can have further severe social and ecological consequences, for example, the displacement of local populations or the contamination of groundwater.
Fertile soils have served humanity as a source of food for thousands of years—worldwide over 90 per cent of foodstuff production directly depends on it. With a growing world population, however, the available area for agriculture per capita is sinking, while at the same time unsustainable agricultural use, polluting contamination, and sealing cause the loss of several million hectares of fertile land every year. It is a precious resource that does not recover quickly. It takes about 500 years for just two centimetres of topsoil to form.
But land plays an important role not only for foodstuff production but also as a filter for rainwater and, consequently, for potable water supply. It also lowers the amount of the greenhouse gas, carbon: Healthy soils can store more CO2 than the earth’s vegetation and atmosphere together, and therefore, against the background of global warming, make a big contribution to regulating the climate. Modern agriculture, in comparison, has a counterproductive effect, as arable land, as a rule, contains fewer organic substances and consequently can store less carbon. Ploughing and harvesting of crops at an industrial scale also release stored CO2. Other greenhouse gases that damage the climate and that arise during industrial agricultural land use are methane, which has an effect 25 times stronger than CO2 and is created in particular in the cultivation of rice and livestock farming, and N2O (nitrous oxide), which is released when nitrogen fertilisers are used.
Sources and further information:
- Soilatlas (2015): Facts and figures about earth, land and fields. (published by the Heinrich-Böll-Foundation, Institute for Advanced Sustainability Studies, Bund für Umwelt- und Naturschutz Deutschland and Le Monde diplomatique).
- Interactive real-time forest monitoring from the World Resource Institute
- Factsheet zum Global Forest Resources Asssesment 2015 der FAO
- Globalagriculture - World Agriculture Report
- Rüdiger Glaser (2014): Global Change, Darmstadt. (German)