SimEarth was a best-selling video game from the 1990s. Through it, I spent many hours avoiding homework and lawn mowing by geo-engineering new versions of Earth and Mars. Constructing a better world through science and engineering is a popular subgenre of science fiction and gaming. And in the real world, we are witnessing a remarkable geoengineering project to transform the Earth into a vast hot tub.
The African Great Green Wall (GGW) is an ambitious reforestation endeavor designed to create a contiguous swath of forest stretching across Africa from Senegal to Djibouti. Spearheaded by the African Union, this initiative spans over 8,000 km and involves 22 African countries. The GGW initiative aims to restore 100 million hectares of land currently facing degradation.
The African Great Green Wall (Sevgart, CC BY-SA 4.0, via Wikimedia Commons)
The initiative's primary objective is to halt the complete desertification of the Sahel region in Africa—a zone bordered by the arid Sahara desert to the north and the more humid savannas to the south. Over recent decades, this area has increasingly adopted desert characteristics, leading to famines, climate change, and widespread regional instability.
As we saw in an earlier WWAT article, surface vegetation significantly affects the atmosphere above it. The aspiration behind the Great Green Wall is to foster a more stable climate in the region that is less prone to extreme variations such as flooding and droughts. Additionally, the project aims to sequester 250 million tons of carbon. It can do this in a number of ways, including:
Evapotranspiration – Vegetation releases water vapor through transpiration, which cools the air and increases humidity. This can influence cloud formation and precipitation patterns.
Albedo – Compared to sandy environments, the darker colors of vegetation can absorb more heat in the day and release it at night (heat capacity). This decreases extremes that can be tough on life.
Wind patterns – The increased roughness of vegetation can impact surface-level wind patterns, limiting erosion.
Climate – Vegetation increases CO2 absorption and sequestration.
Singing - It can inspire polkas about the weather.
Hope can be a powerful drug, but will it match reality? Forecasting the effects of such a vast project on regional weather patterns is complex. Various factors need consideration, including the interconnected nature of climate systems—where increased rainfall in one area might lead to drought in another.
To investigate the implications of the GGW on weather, two researchers in Germany, Dr. Gerhard Smiatek and Dr. Harold Kunstmann, modeled the impact the GGW may have on weather conditions across the region. They started with an existing computer model called the Model for Prediction Across Scales (MPAS), which is a scalable, global climate and weather modeling software package. They simulated changes in vegetation in the regions around the GGW, focusing on its precipitation impact and related variables during the June – September rainy season.
Modeled precipitation change for the entire summer season (left) and only August – the highest precipitation month - (right). It predicts more precipitation to the east and less to the west, but the differences are not significant. (Earth Interactions 27, 1; 10.1175/EI-D-22-0013.1)
What did they find? Not much! The study revealed no significant effects on summer precipitation patterns within the Sahel region, nor any detrimental impacts on adjacent regions. There were minor changes observed in other variables, such as temperature, radiation flux, and rainwater runoff, but these were slight.
Limitations of the simulation include an assumption that the Great Green Wall instantaneously pops into existence as if the Jolly Green Giant harvested it overnight. However, the reality of such a transformation would involve slower, incremental and heterogeneous growth. Furthermore, the models rely on current precipitation trends, which are likely to change in the future due to climate change.
When Nothing is Something
This is an example of a null effect in science – when an intervention (in this case, the creation of the GGW) does not show a predicted effect (in this case, precipitation impact). It is quite common in science, though you wouldn’t know it by looking at research journals. Authors and editors prefer to publish positive results, creating a bias in the scholarship that science is struggling to deal with. Kudos to the authors and the journal, Earth Interactions, for publishing the results. Although not definitive on their own, these results pose ideas and questions that need to be addressed with further research.
Also, beyond its impact on precipitation, there are other possible benefits of the GGW. Ecologically the moderated temperatures may allow some life to more easily adapt to a changing climate. And it could preserve ecosystems serving as a refuge from extreme weather and man-made deforestation. Agriculturally, it could help keep soil healthier and make local weather more predictable thereby helping farmers. And then there is the simple fact that it would likely be a beautiful place and new wonder of the world.
And Now for Something Completely Different
The Great Weather Song Person is Matt Farley. In 2014, he published an album, Meteorology Music for You, which consists of 88 (one for each piano key) songs about weather. The songs are short and catchy with tongue-in-cheek titles like “Look at All this Fog (It’s Ridiculous)” and “Ice Caps are Melting. Someone Do Something!”. If you are a parent, you have likely encountered Mr. Farley through his songs about poop, which are among the most requested songs by children via Alexa. To get my own kiddo to take her baths, I allowed her to listen to these songs in the tub as an incentive. It worked wonders. And for that, I’ll always be in Mr. Farley’s debt.
We acknowledge additional contributions by Dr. Swarndeep Gill.