Vegetation shifts cause land degradation

Climate change causes massive alteration of natural habitats, especially in dry areas where ecosystems are particularly sensitive to land degradation or desertification. This includes shrub species encroaching on productive desert grasslands, a phenomenon brought about by changes in rainfall or land use, as well as soil erosion.

Investigating the grassland-shrubland transitions in desert environments was the aim of the EU-funded initiative VEGDESERT (Vegetation shifts in desert environments: A multi-scale ecogeomorphic approach for the analysis of grassland-shrubland transitions). The team used a variety of methods to capture vegetation dynamics, including remote sensing, soil and plant experiments, and an ecohydrological model for simulating soil moisture.

Scientists found that grass growth was synchronised with the summer monsoon rainfall, while shrubs can sustain vegetation production during both summer and winter. Although the test area showed no significant shrub expansion or grass recovery within the last 15 years, future changes in seasonal rainfall could increase shrub area.

The experiments showed that grass seeds sharply decreased where shrubs dominated; however, modelling revealed that shrub expansion was local and episodic (5- to 10-year periods). Results also suggested that ecosystem interactions play a major role in regulating which species dominate and the rates of plant change at grassland-shrubland transition boundaries.

Overall, VEGDESERT results help to understand the processes regulating the dramatic changes taking place in arid and semi-arid landscapes worldwide. They could also aid in providing practical tools to manage areas threatened by desertification.