Savannahs and climate change

Photo credit: Nature World News

(Photo : © tellmemore / Fotolia)

Savannahs Help Slow Down Climate Change

By Jenna Iacurci

Savannahs, though they are not jam-packed with carbon-absorbing trees, nonetheless help to slow down climate change, according to a new study.

Tropical rainforests have long been considered Earth’s most important carbon sinks, sequestering large amounts of carbon dioxide (CO2) from the atmosphere and thereby slowing down the increasing greenhouse gas effect. But scientists now report in the journal Science that the vast extensions of semi-arid landscapes – including savannahs and shrublands – actually dominate other global ecosystems in carbon capture.

“Understanding the processes responsible for trends and variability of the carbon cycle, and where they occur, provides insight into the future evolution of the carbon sink in a warmer world and the vital role natural ecosystems may play in accelerating or slowing down human-induced climate change,” Anders Ahlström, from Lund University and Stanford University, who led the study, said in a statement.

That’s not to say that tropical rainforests aren’t crucial in the fight against climate change. These ecosystems are highly productive, and fight carbon even better than we hoped, taking the harmful greenhouse gas from our atmosphere at unprecedented rates. However, the downside is that rainforests are extremely crowded with little room to fit in more photosynthesizing plants that can store carbon. In addition, the typical moist, hot weather conditions are ideal for growth and do not change much from year to year.

In savannahs, on the other hand, increased productivity actually makes more room for trees whose growing biomass provides a sink, or store, for carbon sequestered from the atmosphere. In addition, savannahs spring to life in wetter years, causing large fluctuations in CO2 uptake between wet and dry years – large enough, in fact, to control the amount of CO2 in the atmosphere.

Read the full article: Nature World News

Appropriate indicators of land-cover modifications

Photo credit: Pixabay

Monitoring land-cover changes in semi-arid regions: remote sensing data and field observations in the Ferlo, Senegal

by A. Diouf and E.F. Lambin


Dryland degradation rarely translates into linear, declining trends in vegetation cover due to interannual climatic variability. Appropriate indicators of land-cover modifications need to be defined for semi-arid regions.

Our hypothesis is that degradation can be measured by:

  • (1) a decrease in the resilience of vegetation to droughts;
  • (2) a decrease in rain-use efficiency; and
  • (3) a modification of floristic composition.

The objective of this paper is to test the relationships between a remotely sensed indicator of vegetation, rainfall data and field measurements of biomass and floristic composition.

The study was based on field measurements of vegetation conditions covering a period of 10 years, in the semi-arid region of the Ferlo in Senegal.

Our results indicate that land-cover modifications in the Ferlo are best measured by changes in rain-use efficiency. No consistent trend in the relative abundance of grass species was visible at the scale of the decade, even on the two sites affected by degradation. Just after a drought, a given increase in rainfall results in less biomass production than is the case for normal years.

Read the full article: Science Direct

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