What You’ll Learn In This Module
- How does soil affect climate change?
- What is the story about peat bogs and climate change?
- Why care about coastal wetlands?
- What causes soil erosion and soil degradation?
- A growing world population needs quality food.
- How do we protect soil health?
- What is managed grazing?
- What is silvopasture?
- Are biofuel crops a good idea?
How does soil affect climate change?
The soil and climate change are closely intertwined. After the ocean, the soil is the second most important carbon sink on earth. It plays a critical role in helping to reduce climate change.
The land draws down carbon dioxide from the atmosphere and stores carbon. There is currently more carbon stored in our soils than the carbon stored in forests.
But without protection, the carbon in the soil, and the carbon stored in forests and plants, can be lost quickly and sometimes irreplaceably.
Changes in land use, such as drying peatlands to use peat for other purposes, cutting down forests for grasslands, or ploughing up grasslands to grow crops, releases carbon dioxide into the atmosphere.
The chart below shows that between 10% and 15% of global emissions of carbon dioxide have come from land-use change.
This means that the burning of fossils fuels is by far the largest cause of climate change, but the second, still important, source is changes in land use.
What is the story about peat bogs and climate change?
Peatlands are a type of wetland found on every continent. They are something in-between solid ground and water and are very important carbon sink.
Peatlands covers only about 3% of the world’s land surface and yet store at least twice the amount of carbon as the world’s forests.
Some peatlands date back to the last ice age and others have been untouched for thousands of years.
They are a soggy mix of moss, grass and other vegetation slowly decaying below a living layer of plants.
Peatlands are very carbon-rich soils, containing over 50% carbon. When wet and healthy, they draw down and store carbon from the atmosphere, indefinitely.
The water is crucial, since it keeps the carbon from escaping from the peat and into the atmosphere. Plants are necessary for the peat to continue to stockpile carbon.
But the process is not fast.
On average, about 1mm of peat is produced per year. But it can take thousands of years to produce the depths of 1.5 to 2.5 meters found in northern peat bogs.
Peatlands have several additional benefits:
- The rich organic soil holds onto water, so peat soils are helpful in reducing flooding and reducing the effects of drought.
- For example, one common peat bog plant called Sphagnum moss can hold up to 20 times its own weight in water.
- Peat soils improve water quality as the water is filtered by the soil.
- Peatlands are also often areas of stunning natural beauty with huge biodiversity.
However, the carbon in damaged peatlands can also be lost very quickly.
Damaged peat bogs produce 5 percent of global carbon emissions caused by human beings.
Once dried or taken out of their natural habitats, the peat loses its carbon into the atmosphere, contributing to global warming.
For example, when peatlands are drained for agriculture and peat is extracted to be used in garden compost as a garden fertilizer. Peat has also traditionally been removed and burned as a heating fuel.
- Many plant lovers don’t realize that the compost that they buy from a garden centre for their houseplants or gardens is very likely to contain peat.
In the northern hemisphere, close to half of the peat excavated has been used by the horticultural industry for use in bags of compost.
But entirely peat-free composts are commonly available.
- In the southern hemisphere, forest fires and the clearing of peatlands for palm oil and pulpwood are major causes of peatland damage.
Restoring drained and damaged peatland is essential to both reduce emissions and to help tip the balance to peatlands storing more carbon.
- Reflooding these soils is the start of this process.
- These very precious environments need to be better-protected.
- The outright preservation of healthy bogs and the banning of peat removal for garden fertilizer or for heating seems justified.
For parts of the world, peatlands have been sacred places. Some consider them as the gateway to the gods.
Why care about coastal wetlands?
Coastal wetlands are found along the edges of coastlines where the land and ocean meet.
They include the world’s salt marshes, mangroves and populations of seagrasses.
They provide nurseries for young fish, an important line of defence against storms, a natural filtering of the water and they also sequester large amounts of carbon.
This carbon is stored in plants and also in roots in the deep wetland soil.
The rapid plant growth in these areas and the low oxygen levels lead to the rapid buildup of layer upon layer of decaying plant matter, producing carbon-rich soil.
It’s estimated that coastal wetlands store 5 times as much carbon as tropical forests. Mangrove forests store about 22 billion tons of carbon alone.
But while these areas are important for biodiversity, defence of the land and carbon storage, in human history “wetland” has often meant “wasteland”.
Coastal ecosystems have been extensively damaged by being drained and cleared for other land uses, sprayed for mosquitos, polluted with runoffs from the land and had their timber cut. They have been used and abused for the operations of the fuel, plantation, farming, building and other development-related industries.
Keeping coastal wetlands intact and healthy is an essential component of tackling climate change.
It will ensure that they remain a carbon sink, rather than a carbon emitter.
It will also help them cope with the impacts of climate change such as rising sea levels and increased storm activity, helping them to protect local coastal communities and shore-line ecosystems.
What causes soil erosion and soil degradation?
It takes at least 100 years to create an inch of topsoil. But we are losing it at 17 times that rate.
The causes of soil erosion and degeneration are complex. They include:
- Agricultural practices. Modern farm and industrial practices have focused on growing single crop types (monoculture), regularly ploughing or tilling the land, using herbicides to clear weeds, pesticides to clear bugs and fungicides to clear disease. Artificial fertilizers and minerals are added to the soil and the lack of water is compensated by irrigation. These techniques are gradually eroding and exhausting the soil and releasing carbon into the air, while little or no carbon is captured.
- Deforestation. The roots of plants and trees help to anchor the soil and overhead greenery protects it from the wind and strong rains. Clearing land and reducing forested areas and hedgerows leaves the soil more vulnerable to soil erosion.
- Climate change. The increases in drought from climate change will dry up the soil faster, making it more vulnerable to wind erosion. On the other side of the spectrum, the increase in heavy rains and floods from climate change make the soil more vulnerable to erosion by water runoff. Climate change will also bring more violent winds and storms, adding to these problems.
A growing world population needs quality food.
The global population has been increasing by about 83 million people per year, that’s about 1.1% on average. It grew from 1 billion in 1800 to 7.9 billion in 2020.
As the population grows, the world has faced repeated concerns over how we will feed ourselves.
Modern science and agriculture responded, developing intensive agricultural techniques that produced a relatively small selection of foods as cheaply as possible.
The quantity of food has increased significantly. Yet more and more scientific studies are showing that the quality of our food is decreasing and so is its nutritional value.
Some of that research suggests that the higher levels of carbon dioxide in the atmosphere is affecting plant growth, reducing its important minerals.
And the soil has paid a heavy price under modern techniques, as have the water supply, the birds, beneficial insects, human health and the climate.
And there is that old saying… “You are what you eat.”
Starting in the 1980s, people started eating more processed food. And that trend has continued.
Highly processed foods are manufactured using fillers, fats, sugars and starches and including E numbers and other mysterious ingredients.
Instead of eating fruit and vegetables from nature, especially people in the West are eating more synthetic, imitation foods which are mixed in factories.
And some multinational companies have made huge profits from that.
While the developed world has lost touch with eating well, agriculture is also producing too many cereals, starches and sugars, and too little fruit and vegetables.
Human health has suffered.
Processed food producers could produce this food cheaply since they were not charged for the full costs of any damage caused.
These costs included costs to the environment, through land-use changes and carbon dioxide emissions, and costs to humans, through increased obesity, disease and disability.
One problem has been that the cash value of natural lands, such as peat bogs, coastal wetlands and forests is too low compared to its value when used for agricultural and industrial production.
This gives humans a direct incentive to change the use of the land.
Potential solutions to help care for the quality of land use and the quality of food production in parallel include:
- Closing ‘value gaps’. This means adjusting the price of land to include a value for the natural services it is already providing, as providing beauty, capturing carbon and housing biodiversity.
- Using new techniques to better care for the soil. This would ensure the high productivity of croplands over the years, while restoring and increasing the ability of all soils to capture carbon.
- Changing diets towards natural food and away from processed substitutes, while reducing food waste. This would increase health and use agricultural land more efficiently.
- Using existing agricultural land more sustainably and productivity to free-up some of this land for e.g more wetlands or forests to capture carbon.
How do we protect soil health?
It’s estimated that there are close to 300 million hectares of degraded croplands in the world.
And when extensive areas of forest are cut down, the land often turns into less product grassland with a considerably reduced capacity for storing CO2.
Regenerative and sustainable agricultural practices can restore land that has been damaged and degraded.
Such techniques prioritize carbon capture in the soil, aiming to continuously improve and regenerate the health of the soil and the plants growing in it, by restoring the soil’s carbon content.
It includes:
- Growing a variety of crops, not tilling the land, using local and natural fertilizers and no or minimal pesticides and synthetic fertilizers.
- Grasslands are managed and crops are rotated around fields.
- Regenerative agriculture increases the organic matter in the soil, its fertility, texture, water retention and the existence of many microscopic organisms that promote soil health.
- As a result, more carbon is absorbed by the soil, plant health improves along with the nutritional value of the crops and more can be grown.
Plants need a home and bare ground needs a cover.
What is managed grazing?
Grasslands make up 70% of the world’s agricultural land.
Where original grasslands remain intact, they are healthy and full of carbon-rich soil.
But when this land is ploughed over and grazed by domestic animals, the land can degrade over time, releasing the carbon it has stored into the atmosphere.
When the grass is overgrazed by animals, the plants reserves are exhausted, and it dies.
And when this happens, it doesn’t regrow. Instead, the land deteriorates, and its carbon is lost to the atmosphere.
Carefully managed grazing techniques can prevent this from happening.
They improve soil health, carbon draw-down and storage, water retention and grass health.
New managed grazing techniques graze animals on small plots of land, rather than whole fields. They rotate these gazing locations frequently and systematically, increasing the length of time that the land rests before the animals’ return.
Improving grazing in this manner can improve the amount of carbon stored in the soil by between 1.5 and 3 tons per acre.
Case studies have also shown numerous other advantages. These include:
- Native grasses re-establish themselves
- There is less need to resow the grass
- Water management and weed management improve
- Animals are more energetic
- The organic consistency of the soil improves;
- The water absorption and retention of the soil improves.
- Birds and animals return to the area.
- Farming incomes increase.
What is silvopasture?
Silvopasture comes from the Latin words for forest and grazing. It refers to the integration of raising livestock and growing trees.
It includes planting trees in pastureland and letting domestic animals roam in existing forests.
Livestock can include a variety of animals and birds such as sheep, pigs, cows, deer, ducks, chickens and turkeys.
It’s an ancient practice that has been used, for example, in the Iberian Peninsula for feeding pigs on acorns to produce the world-famous ham ‘jamón ibérico’.
It’s now being applied to over 350 million acres worldwide.
Soil is also important for mitigating climate change within this system.
Cattle and other animals that chew their semi-digested food produce roughly one-fifth of greenhouse gas emissions.
Silvopasture helps to counterbalance the methane emissions from livestock, especially cattle and sheep, and to sequester the carbon from methane under the soil.
It provides a number of advantages:
- It’s better than grassland, since it allows carbon capture and storage in both the biomass above ground and in the soil below.
- The combination of land uses brings financial benefits for farmers, as well as diversifying commodity production.
- Treeless livestock pastures may suffer from sun, heat and winds, and hence soil erosion and degradation. In contrast, Silvopasture provides shade, wind protection and food for the animals and helps to prevent soil damage.
- Animal health increases, as does the quality of their meat, milk and offspring.
- Natural fertilizer is good for the trees, reducing the need and cost of any artificial fertilizer.
- The need for weed control is reduced, along with the use of artificial herbicides.
- Healthier land is more productive over time.
This form of land use may become more popular as the climate changes. Trees create cooler microclimates and a more protective environment and can regular water availability.
Are biofuel crops a good idea?
One of the consequences of global warming is the increased use of land for the production of Biofuel.
Whether plants used for bioenergy are annual or perennial makes a big difference.
Annual plants are typically planted in the spring, grow during the summer and are harvested in the autumn.
They live for just one growth cycle and often demand a lot of nutrients from the soil and a lot of attention using modern farming methods.
Perennial plants survive the winter and come back to grow year after year.
They demand much less energy from the soil and can avoid the use of synthetic fertilizers, tilling or ploughing and fossil-fuel-burning farm machinery.
To date, many of the crops grown for bioenergy in developed countries have been annual, government-subsidized and have not benefited the climate because their energy inputs were so high.
But perennial bioenergy crops, using plants such as miscanthus, require less water and nutrients and can be harvested year after year without additional sowing.
Crops of poplar and willow can be cut back close to the grown and they regrow.
Growing these perennial bioenergy crops can have a very different and a positive impact on soil carbon. They can make a net positive impact through sequestration.
Other advantages include preventing soil erosion, less vulnerability to pests and the ability use land which is not suitable for food production.
But biodiversity is an important element that needs to be kept in mind.
Plant species must be multiple and chosen carefully in line with their natural habitats.
Continued monocropping is not a solution for the future.
Moreover, trees such as poplar and willow are allergens to around 20% of the population of some developed countries.
Want to know how forests carbon capture? Read about how trees help climate change.