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Drylands

earth science Maturity 7-9 Next article →

Drylands are unique ecosystems defined by a significant scarcity of water. In these regions, the amount of precipitation is balanced by evaporation from surfaces. Plants also contribute to this balance through evapotranspiration, which is the release of water vapor into the air.

Spiny Forest, Madagascar (23985856889)
Spiny Forest, Madagascar (23985856889)

These areas are complex systems where climate, soil, and vegetation interact constantly. The health of these ecosystems is vital for global biodiversity and human well-being. They also play a role in helping to halt climate change through carbon sequestration.

Fig 1.3.11 Schematic showing key feedbacks that could lead to dryland tipping.
Fig 1.3.11 Schematic showing key feedbacks that could lead to dryland tipping.

Scientists classify drylands into four distinct sub-types based on their level of aridity. The first type is dry and sub-humid lands, which include biomes like grassland savannahs and Mediterranean climates. These areas are highly productive and support many different crops and livestock.

Inda Abba Hadera forest
Inda Abba Hadera forest

The second type is semi-arid lands, where annual rainfall typically ranges between 500 and 800mm. Third are arid lands, which cover approximately 10% of the Earth's land surface. Finally, hyper-arid lands are the driest zones, covering about 8% of the world. These hyper-arid regions often have little to no vegetation and receive very irregular rainfall.

Dry land - panoramio
Dry land - panoramio

Drylands cover a massive portion of our planet, totaling 41.3% of the Earth's land surface. This includes 66% of Africa, 40% of Asia, 24% of Europe, and 15% of Latin America. More than 2 billion people live within these dryland ecosystems. A large majority of these inhabitants live in developing countries, which contain 72% of the world's drylands. In fact, almost 100% of all hyper-arid lands are located in the developing world. However, countries like the United States, Australia, and those in Southern Europe also contain significant dryland areas.

Brazilian semi-arid region
Brazilian semi-arid region

Climate change presents a severe threat to the stability of these environments. Between 1982 and 2015, anthropogenic climate change caused the degradation of 12.6% of the world's drylands. This degradation leads to increased droughts, desertification, and soil erosion. Such changes reduce soil fertility and the ability of the land to sequester carbon. These factors directly impact local agriculture and food security for millions. Currently, land degradation in drylands affects 213 million people, mostly in the Global South.

Fig 1.3.11 Schematic showing key feedbacks that could lead to dryland tipping.
Fig 1.3.11 Schematic showing key feedbacks that could lead to dryland tipping.

Recent decades have seen a dramatic shift in global landscapes. About 7.6% of global land has transitioned into drier conditions. This means land has either become more arid or shifted from non-drylands into drylands. This shift is equivalent to an area half the size of Australia transforming from humid to dry. In semi-arid lands, climate change manifests through increased precipitation variability. This includes shorter rainy seasons and more frequent, violent wind events. Such weather patterns can prevent the buildup of necessary soil moisture.

In regions like East Africa, people have developed specific ways to survive. Many rural inhabitants are pastoralists who rely on cattle for their economic and cultural well-being.

Cueva de los casares 07
Cueva de los casares 07

To manage scarce resources, they use strategic movement to find pasture during the dry season. They may also reduce herd sizes or change how they manage water. In some countries like Burkina Faso, Senegal, Mali, and Kenya, people are also becoming proactive by engaging in trade and transport. These adaptation strategies help communities remain resilient despite unpredictable rainfall.

Restoration is a key tool used to protect these vital ecosystems. The International Union for Conservation of Nature (IUCN) defines restoration as actions that protect or recover natural ecosystems. This can be done by restoring degraded areas to their previous functional state. It can also involve preventative management to support ongoing ecosystem services. One major example is the Great Green Wall project in the Sahel region.

Drivers of Restoration Outcomes in the Colorado Plateau
Drivers of Restoration Outcomes in the Colorado Plateau

By using sustainable land management and climate-smart agriculture, we can help mitigate the impacts of desertification.

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🖼️ Images & Media (8)
File:Cueva de los casares 07.JPG
Cueva de los casares 07.JPG
File:Fig 1.3.11 Schematic showing key feedbacks that could lead to dryland tipping..png
Fig 1.3.11 Schematic showing key...
File:Spiny Forest, Madagascar (23985856889).jpg
Spiny Forest, Madagascar (23985856889).jpg
File:Brazilian semi-arid region.jpg
Brazilian semi-arid region.jpg
File:Inda Abba Hadera forest.jpg
Inda Abba Hadera forest.jpg
File:Arid chaco.jpg
Arid chaco.jpg
File:Dry land - panoramio.jpg
Dry land - panoramio.jpg
File:Drivers of Restoration Outcomes in the Colorado Plateau.jpg
Drivers of Restoration Outcomes in the...
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