Soils And Climate Change

Soils are a crucial part of climate action. They are the biggest natural sinks, second to oceans and bigger than forests. They form part of the carbon cycle. Therefore, good soil management is part of climate action.

Soils carry a reserve of carbon that is 2500 gigatons, more than what is in the air or stored by green plants.

According to the Food and Agriculture Organization, the first 30 centimeters of soil holds double the quantity of carbon dioxide in the air. Additionally, a third of the world’s soils are degraded soils.

Although all soil stores carbon, the specificity of soil type controls the amount that can be stored. Clayey soils, rich in aluminium and iron, locks in more carbon because they offer a larger surface area. Soils of volcanic origin also contain higher carbon content.

Permafrost is the frozen soil beneath the ground. Permafrost means permanently frozen (frost) soil. Such soil types are usually frozen from beginning of the year to its end, no matter the season. They are found on the tops of mountains (mountain ice caps) and Polar Regions, the Antarctic and Arctic.

Typically, when temperatures drop below the 0 degree line, all water and moisture in the ground freezes and becomes solid. This results in hard and stable ground with the soil mass expanding considerably. Permafrost holds massive reserves of organic matter, from thousands of years of plant and animal remains. Because of the very low temperature, soil microorganisms cannot carry out natural decomposition processes.

With climate change, these areas are affected considerably, especially the Arctic. Rising atmospheric temperatures affect ground temperature as well, and thawing of the ground occurs. The ice in the soil turns to water and this has several consequences. One is that long frozen microbes once more have the ideal conditions to function and organic decomposition begins again. This releases two gases of major consequence: carbon dioxide and methane. Both are potent greenhouse gases adding to the stores that are already in the atmosphere and so further warm the climate.

Two is that as warming continues and the Arctic particularly thaws, the more carbon is produced, the more the global warming increases and the more the Arctic thaws. It feeds upon itself. It leads to a self-propagating loop which is bad news for climate.

Another consequence is the collapse of built infrastructure. As ground ice turns to water, the ground shrinks on itself and its mass is reduced. This affects the integrity of all physical infrastructure built on it.

Therefore, as a matter of urgency and economic consequence, it is important to cut climate warming emissions.

Mangroves are the forests that grow along the boundary between the ocean and rivers. They flourish at the mouth of rivers, at the confluence between the two water systems. They are unique ecosystems for many reasons. First of all they live in brackish water, where there is a mixture of saline and freshwater. The ground beneath them is waterlogged so they cannot obtain soil oxygen. They instead have breathing roots referred to as pneumatophores.

Mangroves are coastal forests and offer all the services of forests such as climate regulation and carbon sequestration. But especially in the case of these forests, they also clean up the water and remove polluting substances. They protect areas further inland from destructive storms and storm surge. They also offer spacious habitat for fish nurseries, for breeding and the hatching of fingerlings. They are known for very unique flora and fauna such as one of a kind butterflies. An example is the Arabuko Sokoke forest in the Kenyan coast.

Despite their small acreage compared to terrestrial forests, mangroves sequester four times the carbon dioxide compared to the other forests. They are very efficient at carbon storage and the soil sediment beneath them carries about 6.4 billion metric tons of carbon. Mangroves however are under threat from agriculture and shrimp and prawn farming. Sea level rise also threatens to submerge them.

Grasslands are another type of terrestrial ecosystem that are super carbon stores. They are some of the most efficient carbon stores because they have the capacity to spread wide in a short space of time and are hardy. They also colonize new areas with ease. They are prime habitat for wildlife, an example being the African savannah grasslands like those found in the Tsavo and Maasai Mara wildlife protected areas. These game reserves and national parks house the famed Kenyan wildlife including the Big Five. They are especially important because they store their carbon under the ground and so are unlikely to be touched by fire or affected by clearing per se. This happens through their extensive root formations. Did you now that most of the grass body is found beneath the soil?

Also, their extensive fibrous roots can spread from a few centimeters to two or three feet beneath the ground. Grass roots are very dense. This means that when this grass dies, all that organic matter and its carbon value remains below the ground. Dead grass also offers fertile manure for new growth and so the cycle continues. It is argued that grassland soils hold even more carbon reserves than forests.

Savannah grasslands cover one fifth or 20% of the planet’s surface. Therefore, they perform an important role in carbon sequestration and thus climate action. They also are important for biodiversity conservation.

Conversion of these soils to croplands is one of the biggest sources of land use change emissions and causes the loss of vast stores of soil carbon.

It goes without saying that natural ecosystems such as grasslands are not idle land. They perform major environmental functions which is the reason why interference with these systems should be banned.

Peatlands consists of swamps and bogs and marshes. They cover 3% of the earth’s surface. They are ecosystems that are land based but are constantly under water in one form or another. They are wetlands so to speak. Because they are acidic and lack oxygen, all the organic matter that dies in these areas does not decompose and so is left intact. The accumulation of these plant and animal bodies over thousands of years makes peatland soils very rich in carbon.

Peatlands are however facing threats from clearing and draining for agriculture and mining leading to the release of tons of carbon dioxide into the atmosphere. Alongside mangrove forests, they are cleared especially for cocoa and palm oil plantations. This is in turn fueled by the commercial demand for these plants, whose products form some of the major ingredients for the multibillion fashion and cosmetics industries and the food industry.

Chocolate for example is from cocoa trees. Palm oil is one of the ingredients of lotions and creams.

Peatlands account for slightly more than 40% of soil carbon stocks. Exploited peatlands release 6% of global carbon dioxide emissions.

Such sensitive carbon sinks should be legally protected.

Croplands by virtue of being covered by green plants store carbon as well but only for a short time. All the carbon absorbed by growing plants is released back into the atmosphere when these plants are harvested and processed for food. Additionally, tilling of land releases soil carbon into the air. Agriculture in its current form releases emissions from farm machinery, fertilizers and soil inputs as well as soil carbon. But of note is that this is case for big plantation farms and not as much for smallholder farms. Fossil fuels are still the biggest source of greenhouse gases and are hugely responsible for the current human driven climate change.

Africa, supported by rainfed agriculture for thousands of years is only responsible for 3% of global emissions but leads the climate action space, a good example being Kenya.

Mulching, cover crops, crop rotation, multiple cropping, conservation agriculture and agroforestry are some of the ways to be climate smart about agriculture and not only do they improve soil fertility, they also increase soil carbon stores.

Rainforests are another part of soil carbon. The Congo Basin rainforest covers 180 million hectares and spreads over 6 African countries. It is the second biggest after the Amazon and is one of the major lungs of the planet. Put together, forested areas store a third of all carbon stores found in dry land ecosystems. They offer other ecosystem services such as clean air, being sources of rivers, micro climate regulation, wildlife habitat, biodiversity protection and others. Considerably, larger amounts of forest carbon stores is above ground, in the vegetation itself. However, below ground stores are extensive, especially in forests which are cover large spaces.

Acidic conditions and lack of soil oxygen are some of the factors that increase soil carbon stocks. Large forests receiving high precipitation, especially the close canopy ones like the Congo forest, contain layers of very carbon rich and fertile topsoil and hummus because of all the partially decomposed layers of leaf litter.

According to NASA, 85 billion tons of carbon is found in the forests of the Democratic Republic of Congo alone. In 2017, the world’s biggest tropical peatlands was found underneath the Congo Forest. The massive rainforest contains the largest underground peatlands.

The first 30 centimeters of the soil (topsoil) is what holds the bigger part of soil carbon. When vegetation is cleared and the soil disturbed through activities such as urbanization and agriculture, this layer is loosened and can be washed away by water or blown away by wind erosion. In this manner, the reserves of carbon locked therein are lost.

Another way that climate change might indirectly cause loss of organic soil carbon is by leaching when flooding occurs. Floods are more frequent with climate change.

Additionally, fertile topsoil washed into waterways causes massive growth of algae and the eventual eutrophication of waterbodies. Eutrophication is the uncontrollable growth of algae in waterbodies due to excess fertility or nutrient levels. It eventually kills off marine life.

The management of soil carbon as a standalone issue is not covered in a clear and comprehensive way by the Paris Agreement. Parts of it however fall under the reduction of agricultural emissions without negatively impacting food production, which is one of the aims of the pact.

The issue can also be touched on in land use and land use changes.

However, in 2015, the French government hosting COP21 launched the 4 per 1000 initiative. It proposes that an increase of 4% of carbon absorption and sequestration by soils especially in agricultural zones would be an effective tool in climate mitigation. This initiative is part of the Global Climate Action Plan and the Lima-Paris Plan of Action.

Soil carbon is vital for the planet’s wellbeing, because proper management of these assets can be an easy and natural way to reduce atmospheric concentrations of carbon dioxide and therefore stop climate change.