- Harnessing the untapped potential of terrestrial ecosystems
- > Terrestrial ecosystems store significantly less carbon than the oceans. Nevertheless, they can make a valuable contribution to the fight against climate change. We must protect existing forests, grasslands and wetlands to this end, engage in large-scale ecosystem restoration and return to sustainable methods of farming and forestry. We’ve known how to do this for a long time. The only thing that’s missing is the will to actually do it.
Forests, grasslands and soils as carbon stores
Solutions implemented far too rarely
The terrestrial carbon stores are much smaller than the oceanic carbon stores. Oceans store ten times as much carbon than is contained in terrestrial organisms and soils. Nonetheless, there are several reasons why the land carbon balance (soils and terrestrial vegetation) plays a key role in the current climate crisis.
Human societies have always contributed to the depletion of land carbon stocks through land-use change. This kind of depletion occurs wherever forests are cleared, be it by fire or otherwise. It also happens when wetlands are drained, natural grasslands are converted to arable land or soils are depleted by intensive agriculture. Each of these activities burns or results in the decomposition of organic matter, thus creating and releasing greenhouse gases. Carbon dioxide emissions from land-use change currently account for about one-tenth of all carbon dioxide emissions attributable to human activities. In addition, methane and nitrous oxide emissions from livestock farming and from the intensive use of fertilizers are on the increase.
Globally, humankind has so far converted 75 per cent of all original land areas and has destroyed 85 per cent of the wetlands that once existed. This has not only altered local climatic processes. It has also had the further effect of reducing the capacity of the remaining ecosystems to absorb and store carbon. The world’s terrestrial vegetation and soils do however still function as a carbon sink, i.e. they absorb more atmospheric carbon dioxide and store the carbon it contains than they release through counteracting processes.
This characteristic means that terrestrial vegetation, and especially forests, has absorbed roughly 31 per cent of our carbon dioxide emissions since 1850 and stored them below ground and in its biomass. Scientists have also been observing a fertilization effect of the rising atmospheric carbon dioxide concentration, which leads to terrestrial plants showing improved growth and steadily taking up and storing more carbon overall.
Based on this knowledge, a number of solutions have been developed that can largely prevent further greenhouse gas emissions from land-use change, increase the size of the land carbon sink and compensate for anthropogenic emissions remaining after all emissions reduction options have been exhausted.
In essence, it is about protecting existing forests, wetlands and grasslands, restoring destroyed ecosystems and soils, practising agriculture and forestry in an environmentally friendly way, and producing enough biomass so that part of it can be devoted to bioenergy generation and the manufacture of goods.
Not all measures are without risk, and competition for land is fierce in some places. Properly implemented, however, known methods could achieve roughly 20 to 30 per cent of the greenhouse gas emissions reductions and carbon dioxide removal needed by 2050 to keep global warming to below two degrees Celsius.
But thus far these have been implemented on far too small a scale. The Intergovernmental Panel on Climate Change attributes this failure to a lack of investment and political, institutional and societal support. There is thus a clear disconnect between our lived reality and the scientific insight and recognition that humankind can only overcome the climate and biodiversity crises with the help of healthy and functional ecosystems.