Africa’s ‘Great Green Wall’ initiative, a massive tree-planting programme expanding to 8,000 kilometers across the Sahel aimed at mitigating desertification in the region, could intensify and bring more rains from the West African monsoon (WAM) and could have an impact as well to other parts of the world, according to a new climate study.
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The Great Green Wall started in 2007 by the African Union has achieved 15 per cent of its target and aims to achieve implementation by 2030. The initiative is considered by countries involved to be contributing to the UN Sustainable Development Goals (SDGs) by providing food security and jobs.
However, scientists from the University of Quebec in Montreal (UQAM) have found from high-resolution regional climate simulations that the re-greening of the Sahel, which previously had experienced a rich vegetation, may change the strength of the WAM which could lead to extreme climate in northern Africa. The study cited that in the Sahara and Sahel region, rainfall is closely identified with the WAM which sustains the lives of millions of people living in sub-Saharan Africa.
Based on research, the ‘Green Sahara’ or the African Humid Period existed following the dramatic changes in WAM 12,000 to 5,000 years BP. This was due to increased summer rainfall which then resulted to the expansion of North African lakes and wetlands, as well as grasslands and shrublands which are now currently a desert.
The researchers presented how the massive vegetation alters the land cover and the associated dust emission and its impact on the strength of WAM, as well as influence other climate patterns such as the El Nino-Southern Oscillation, tropical cyclones, and the Artic climate.
Francesco S.R. Pausata, professor at the Department of Earth and Atmospheric Sciences at the UQAM, explained that in the past the WAM variations were based on the cyclical changes in the Earth’s orbit which affects the amount of solar radiation absorbed by the region. However, these are not sufficient considerations as scientists now also recognize the impact of changes in plant cover and the dust in the atmosphere in monsoon shifts.
Other researchers not involved in the study such as Deepak Chandan of the University of Toronto has pointed out that as more vegetation takes place, a local pool of moisture is created, and with more water cycling from soil to atmosphere. This increases humidity and therefore rainfall.
While the ‘Great Green Wall’ may sound like a great plan aimed at helping millions of people benefit from the project, little study has been done to its possible impact on the climate. Pausata noted that its needs to be further studied, saying that such project is essentially a type of geo-engineering and thereby all possible impacts must be studied.