Reforestation is a common feature in climate change plans, which aim to sequester carbon from the atmosphere. But there is another type of natural carbon sink that is overlooked: peatlands, he writes. Mauro Lourenco.
Ask most people what they picture when they think of natural “carbon sinks” (ecosystems that absorb and store greenhouse gases) and they’ll probably describe a forest. Reforestation is a common feature of climate change plans.
But there is another, equally important type of natural carbon sink that is often overlooked: peatlands. These are a particular type of wetland ecosystem in which a dark, clayey peaty soil is produced. Peatlands store more carbon than all the world’s forests combined.
And they do more than store carbon. They conserve biodiversity, purify water, and reduce flooding and soil erosion. They also play an important role in agriculture: they are good at planting certain crops, such as potatoes and carrots.
Despite this, even the world’s scientific bodies have not paid much attention to peatlands until very recently. Global maps and peatland inventories are inconsistent, although there is more data for the Northern Hemisphere compared to the Southern Hemisphere and the tropics. High-quality data on the extent of peatlands is only available for a small selection of countries and regions, including Canada, Sweden, and Western Siberia.
This gap must be filled urgently: new peatland deposits need to be discovered, quantified and protected in an uncertain climate future that depends on natural and intact carbon sinks.
This is why, for my PhD, I set out to quantify and map recently discovered peatland deposits in the Angolan highlands, which have been drastically understudied. This region is hydrologically and ecologically important. One reason is that it is the main source of water that flows into the Okavango Delta, a UNESCO world heritage site, in northwestern Botswana.
The Okavango is a flat, extensive, and seasonally inundated alluvial fan that is one of the few large inland delta systems that does not drain into the ocean. Instead, it flows into the desert sands of the Kalahari Basin.
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I worked together with my PhD supervisors, Professor Jennifer Fitchett and Professor Stephan Woodborne, using remote sensing to estimate that there are around 1,634 km², or approximately 230,000 full-size football pitches, of peat bogs in the uplands. from Angola.
This is a conservative figure, since the mapped area covers only 16% of the Angolan Highlands and 4% of Angola. For comparison, the largest deposit of tropical (and African) peatlands, which was also recently mapped in the Democratic Republic of the Congo in the Congo Basin, spans 145,000 km².
This is the first estimate of peatland cover in Angola. And the study reveals potentially more tropical peatland deposits to discover in the upland region and surrounding river basins.
remote mapping
In 2015, National Geographic’s Okavango Wildlife Project was launched to create a network of new protected areas to conserve the length of the Okavango watershed. He has been researching and collecting scientific data on the river system and working with local communities; NGO; and the governments of Angola, Namibia and Botswana to ensure the permanent and sustainable protection of the great Okavango watershed.
The Okavango Delta is dependent on rainfall that occurs in the central highlands of Angola, where water flows south into the Okavango River from two tributaries: the Cuito River and the Cubango River. The Greater Okavango Basin encompassing these three rivers covers approximately 112,000 km² and spans three countries: Angola, Namibia and Botswana.
The water sources come from areas that experienced historical conflicts and wars, and remain unprotected by law. The National Geographic Okavango Wilderness Project was created out of concerns about threats to the Angolan Okavango Basin region and possible downstream consequences for the Okavango Delta.
During pioneering scientific explorations, the project team identified extensive deposits of peatlands in the Angolan highlands. These were the first known scientific explorations of these source rivers and lakes; New species of plants and animals were discovered. The identification of peatlands was also a novelty. In June 2022, I was invited to be part of the research team of the Lungu Bungu River Expedition in Angola.
The author at work (after Covid lockdowns) extracting peat soil on the Lungu Bungu river transect. Jen Guyton
For my PhD, which I started in January 2020, I planned to do extensive fieldwork in the Angolan highlands to quantify newly discovered peatlands. But by April 2020, the world was largely in lockdown due to the Covid-19 pandemic. It seemed that I had no chance of reaching my study site.
Then I was introduced to Google Earth Engine, a powerful cloud computing platform for Earth observation, science, and analysis, and found that I could collect an incredible amount of geospatial data about my study site from home.
Peatlands have unique characteristics that distinguish them from the mainland. Geospatial scientists use multisensory approaches. Optical, radar and LiDAR satellite imagery is used to identify and distinguish peatlands from other wetland features.
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Peatlands have also been mapped based on their geophysical properties, including vegetation cover, topography, and the presence of standing water. I drew these data categories for the Angolan Highlands from Google Earth Engine. I then iteratively went through them over multiple Zoom calls with my supervisors.
All of this data was overlaid and Google Earth Engine’s machine learning algorithms were used to produce the first peatland classification map in the Angolan highlands.
Valuable information
Angola, like many other African countries, is highly vulnerable to climate change. Preserving these important peat bog deposits will help facilitate carbon sequestration. This will allow nature to reduce greenhouse gas concentrations in the atmosphere for free.
The identification and mapping of these peatland deposits will also help facilitate the preservation of the Angolan Highlands region. The health and ecological functioning of these peatlands have direct implications for the local communities that depend on the peatlands for water purification, fishing, cultivation, and fuel.
Mauro Lourenço, PhD student, University of the Witwatersrand
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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