How we transform the landscape and exceed the planetary boundary
In the past 50 years, humanity has converted huge forested areas into farmland – including half of Germany’s surface area. As built-up areas expand and agriculture becomes both more extensive and more intensive, landscapes are transformed, important ecosystem functions are lost, soils are degraded, and biodiversity is diminishing.
With activities like logging and agriculture, humanity is transforming the landscape at a breathtaking pace that exceeds our planet’s capacity to adapt. As a result, the biosphere, i.e. the zone of all life on Earth, is under increasing strain from our interventions. The ability of soils to store water is also diminishing. Biogeochemical cycles, e.g. the nutrient budget in soils, are being thrown off balance. Large amounts of fertilizer are used to boost agricultural production; some of that fertilizer is carried into the oceans by rivers, where it disrupts marine ecosystems and can even lead to zones where life is nearly impossible due to lack of oxygen.
Johan Rockström, who developed the planetary boundaries concept, and a team of scientists proposed in 2009 that no more than 15 percent of Earth’s ice-free land area should be used as farmland. In the Amazon rain forest, this figure is thought to be 20 to 25 percent. This means a substantial portion of natural woodlands must be preserved along with their ecosystems to avoid overtaxing the Earth system’s natural capacity of self-regulation.
In 2015, it was found that forests only grow on 31 percent of the world’s ice-free land and that 37 percent of the land area is used for agriculture. This means the planetary boundary has been exceeded, with agriculture using the greatest percentage of ice-free land.
Land use and the transformation of land systems have a special role in the planetary boundaries concept, because excessive land conversion also affects other boundaries: biodiversity, biogeochemical cycles, and the hydrological balance. To learn more, see the home page of our Planetary Boundaries series.
How the forests can be protected
The distribution of woodlands and the intensity of land system transformation are very complex. However, in order to ensure that the largest possible area retains its original function, it makes sense to mainly use Earth’s most productive areas with high-yield soils. Since that would result in less overall land use, it would be a way for us to permanently return to the safe operating space.
How can we return to the safe zone?
We have clearly already overstepped the planetary boundary for land use. Most importantly, vital woodlands like the Amazon rain forest have lost some of their ecosystem functions. To avoid exceeding this planetary boundary even further, we should only use land when there is no alternative. For example, a sustainable, low-meat diet can help to reduce the amount of land needed for agricultural production.
Sustainable agriculture and other measures can help to counteract the loss of productive land and regulate the natural hydrological balance. Of course, some land will still be needed for urban development, energy crops for biofuels, and other uses.
What consequences can be expected for the climate?
A sharp decrease in woodlands has an impact on the climate, because natural forests are an important component of Earth’s climate system that can counteract climate change. Large-scale deforestation in the Amazon region is converting a carbon sink that absorbs carbon dioxide into a source of greenhouse gas emissions that has a negative impact on the climate.
If Earth’s forests absorb less carbon dioxide, larger amounts will remain in the atmosphere, leading to higher temperatures and reinforcing climate change. Moreover, changes in soil structure after deforestation could exacerbate droughts and flooding in extreme weather situations.
Scientific editing: Rico Fischer and Friedrich Bohn, Helmholtz Center for Environmental Research.
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