Erosion caused by water flow wearing down soil surfaces could rise by up to two-thirds compared to today, according to a JRC-led study that modelled changes until 2070.
In a worst case scenario, with agricultural practices remaining the same as today and no additional policies implemented to limit global warming, yearly soil loss could reach roughly 71.6 petagrams – a 66% increase compared to today. One petagram is equal to one billion tonnes.
Soil is important as it is the very basis for the food we grow as well as for the production of feed, textiles, wood and other materials.
It provides us with clean water, hosts biodiversity, recycles nutrients, regulates climate and is part of our landscapes and cultural heritage.
While previous regional studies using similar models already predict increasing loss of soil, they did not point to loss on the same scale as this study.
The Global South is estimated to bear the brunt of the erosion. Rich countries with high fertiliser use and moderate climates can expect erosion at a lower rate.
Without additional efforts to protect soil, this erosion would make reaching the Sustainable Development Goals, including the target of land degradation neutrality by 2030, and above all the elimination of hunger, much more difficult.
A host of knock-on effects
Soil is already under pressure from deforestation, overgrazing, ploughing and unsustainable agricultural practices.
Trends such as surging meat consumption, global population reaching 9.4 billion by 2070, and climate change inducing a more intense water cycle put them under even more strain.
On our planet, where approximately 38 % of land is used for cultivation, soil erosion triggers several unwanted effects.
Erosion makes soils less fertile, as they lose nutrients like nitrogen, phosphorus and organic carbon.
Farmers are pushed to use fertilizers in compensation, resulting in a heavier economic and environmental burden caused by food production, aggravating food insecurity.
Economically vulnerable tropical countries, including Peru, Brazil, a number of states in Western Africa, Cameroon, Ethiopia, Somalia, Kenya, Yemen, Southern Pakistan, India, Myanmar, Southeast China, Philippines and Indonesia are projected to be hit particularly hard by increased soil erosion, the study claims.
Their drive to provide food to all will be an even steeper uphill struggle.
Through erosion, soils’ ability to store carbon is impacted as well, making them less capable of mitigating warming caused by soaring emissions.
Biodiversity and ecosystem stability are also affected.
Rivers will carry more sediments, diminishing the storage capacity of reservoirs and impairing the quality of the water collected in them.
Attaining the Sustainable Development Goal of ‘Clean Water and Sanitation’ and ending the scourge of deaths caused by contaminated water – 6 % of the total in low-income tropical countries – will be more difficult.
The Sustainable Development Goal of ‘Life Below Water’ could be compromised as well, as sediments put the cover of coral reefs in jeopardy.
Change of tack needed
The model used by the scientists involves remote sensing, interpolation techniques and statistical cross-checking. This is the first time it has been used to gain an estimate of future soil erosion at the global level.
Data on land use and climate change that will be used in next year’s report of the Intergovernmental Panel on Climate Change (IPCC) fed in to the model.
Just as the IPCC report, this study highlights the importance of action on soil sustainability. “Given the growing challenge of soil erosion, it is important to act now, act fast and act comprehensively”, the authors of the study say.
Merely carrying on will not yield the desired results. Current conservation agriculture practices will only reduce the projected soil erosion rate by 5 %, the study points out.
There is a lot that can be done. Planting trees next to agricultural land, the practice of crop rotation and building up the vegetative cover are all proven ways of keeping soil erosion in check.
But the policy should not have a narrow focus on fighting erosion alone. The increase in water erosion is mainly driven by the more vigorous water cycle triggered by climate change, suggesting that an all-encompassing approach is necessary.
What the EU is doing to protect soil
The JRC uses advanced modelling techniques, indicators and scenario analyses to provide soil information on the major threats to soil identified in the Thematic Strategy for Soil Protection: erosion, decline of organic matter, compaction, salinisation, landslides, sealing, contamination and loss of soil biodiversity.
The Commission will adopt a new Soil Strategy in 2021 to address these issues in a more comprehensive way and to fulfil EU and international commitments on land degradation neutrality.
Environmental care, climate change action, and landscapes and biodiversity preservation are three of the nine objectives of the future Common Agricultural Policy.
The future CAP will help the sustainable management and efficient use of our soils using an evidence-and performance-based approach.
The European Green Deal, targeting carbon neutrality by 2050, should also mitigate soil erosion indirectly, thanks to its positive effect on the water cycle.
PNAS research article: Land use and climate change impacts on global soil erosion by water
- 25 elokuu 2020