The World’s Degraded Lands

Mapping the World’s Degraded Lands

Using an in-depth review of available databases and resources, Holly Gibbs and J.M. Salmon at the University of Wisconsin-Madison have constructed one of the most detailed maps available of degraded lands across the globe. The main challenge for the researchers was developing a way to effectively bring together a wide variety of disparate data and methodologies. Even the term degraded can refer to many different conditions resulting in lost productivity of the land, including ecological degradation due to invasive species, desertification, or salinization and erosion of soil. The authors standardized four major degradation databases, mapping the data at a resolution of 20 square kilometers (below). The authors eliminated areas with minimal degradation according to each database.

map of degraded lands
Proportion of land area considered degraded according to four different databases and methodologies. All data was standardized to a 20km grid.

A comparison of four major land degradation models (above) showed a high level of spatial variability and uncertainty. The total amount of degraded lands across the globe varied from less than 1 billion hectares (100×100 meters) to over 6 billion hectares. There were, however, several regions with concentrations of degraded lands according to two or more of the models. The map below considers all four major data models together to identify the areas most likely to exhibit a high degree of degradation.

composite map of global degraded land
Percent of area degraded when considering all four major databases.

Regions of Earth’s land area that stood out as among the most degraded included eastern areas of China, Southeast Asia, Central Africa, Western Russia, Southern Mexico, the upper Midwest in the U.S. and north into Canada, and the Pampas of Argentina (a large agricultural region known for its vast cattle ranges). Much of these territories are being over-utilized and suffer from soil erosion, salinization, and other forms of degradation. The identification of degraded lands is a fist step toward potentially rehabilitating these areas for more efficient use. In a world of scarce land resources and constant pressures for additional land leading to deforestation, the opportunity to procure more land through rehabilitation and re-use may represent a viable lower-carbon pathway.

Original Article: Mapping the World’s Degraded Lands

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