**5. The role of soil carbon in different ecosystems**

The carbon in soil plays significant roles in different ecosystems. Some of these include:

#### **5.1. Mitigation of climate change**

The continuous increase in the concentration of carbon dioxide (CO2 ) and other GHGs in the atmosphere largely due to anthropogenic sources is believed to be responsible for climatic changes and related consequences being experienced across the globe [21, 23].

This situation has generated interest in developing strategies for reducing GHGs build up in the atmosphere.

Out of the approximately 8.7 Gt C/year being emitted into the atmosphere, from anthropogenic sources, only 3.8 Gt C/year remains [5, 32]. The unaccounted difference of 4.9 Gt C/year is believed to be sequestered in terrestrial (oceans, forests, soils, etc.) bodies which is referred to as the 'missing sink' [32, 33]. This realization has generated interest on the potential of terrestrial sector (including soil) to sequester carbon in long-lived pools thereby reducing the amount that is present in the atmosphere [3, 4, 13, 14].

#### **5.2. Sustainable land management**

Apart from reducing the concentration of greenhouse gases (GHGs) in the atmosphere, soil carbon sequestration also complements efforts geared at improving land (forest or agricultural land) productivity. This is because all strategies that sequester carbon in soil also improve soil quality and land productivity by increasing the organic matter content of the soil. Organic matter improves soil's structural stability, water-holding capacity, nutrients availability and provide favorable environment for soil organisms [13].

Carbon sequestration activities offer an opportunity for regaining lost productivity especially under agricultural systems. It has been reported that managed ecosystems such as agriculture have lost 30–55% of their original soil organic carbon stock since conversion [7]. The lost productivity of agricultural and degraded lands together offers an opportunity for recovering 50–60% of the original carbon content through adoption of carbon sequestration strategies [13].

#### **5.3. Ancillary benefits**

**4.3. Carbon stock in agricultural soils**

8 Carbon Capture, Utilization and Sequestration

current annual emissions of 8–10 Gt/year [31].

**5.1. Mitigation of climate change**

**5.2. Sustainable land management**

the atmosphere.

ing atmospheric carbon in the soil for a long period of time [8].

**5. The role of soil carbon in different ecosystems**

The continuous increase in the concentration of carbon dioxide (CO2

amount that is present in the atmosphere [3, 4, 13, 14].

provide favorable environment for soil organisms [13].

changes and related consequences being experienced across the globe [21, 23].

According to the IPCC agricultural soils have the potential of sequestering up to 1.2 billion tonnes of carbon per year. However, it has been estimated that already about 50% of agricultural soils have been degraded globally, a situation that creates an opportunity for sequester-

The potential of sequestering carbon in agricultural land is huge as over one third of the world's arable land is in agriculture [30]. Agricultural land could sequester at least 10% of the

The carbon in soil plays significant roles in different ecosystems. Some of these include:

atmosphere largely due to anthropogenic sources is believed to be responsible for climatic

This situation has generated interest in developing strategies for reducing GHGs build up in

Out of the approximately 8.7 Gt C/year being emitted into the atmosphere, from anthropogenic sources, only 3.8 Gt C/year remains [5, 32]. The unaccounted difference of 4.9 Gt C/year is believed to be sequestered in terrestrial (oceans, forests, soils, etc.) bodies which is referred to as the 'missing sink' [32, 33]. This realization has generated interest on the potential of terrestrial sector (including soil) to sequester carbon in long-lived pools thereby reducing the

Apart from reducing the concentration of greenhouse gases (GHGs) in the atmosphere, soil carbon sequestration also complements efforts geared at improving land (forest or agricultural land) productivity. This is because all strategies that sequester carbon in soil also improve soil quality and land productivity by increasing the organic matter content of the soil. Organic matter improves soil's structural stability, water-holding capacity, nutrients availability and

Carbon sequestration activities offer an opportunity for regaining lost productivity especially under agricultural systems. It has been reported that managed ecosystems such as agriculture have lost 30–55% of their original soil organic carbon stock since conversion [7]. The lost productivity of agricultural and degraded lands together offers an opportunity for recovering 50–60% of the original carbon content through adoption of carbon sequestration strategies [13].

) and other GHGs in the

Apart from climate change mitigation and improving forest land productivity, carbon sequestration in soils (of different ecosystems) also have several ancillary benefits. Some of these include: improvement in water holding capacity and infiltration, provision of substrate for soil organisms, serving as a source and reservoir of important plant nutrients, improvement of soil structural stability among others [13]. According to [34] the environmental benefits associated with soil carbon sequestration is 40–70% higher than the productivity benefits. Based on these reasons, therefore, any policy, strategy or practice that increase soil carbon sequestration also generates these benefits.

#### **5.4. Carbon inventories**

The obligation on countries, that are parties to the UNFCC, to deposit their independent nationally determined contributions (INDCs) requires a comprehensive estimation and valuation all carbon sink and sources in the terrestrial and other sectors. These estimation and valuation of carbon in the LULUCF sector will be incomplete if the contribution of soil carbon is excluded due to its large percentage (36–46%). Carbon inventory is a process of estimating changes in the stocks (emission and removals) of carbon in soil and biomass periodically for various reasons [35].
