Journal of Environment and Earth Science www.iiste.org ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online) Vol.10, No.8, 2020 32 A Review Paper on the Role of Terrestrial Carbon Stocks for Climate Change Mitigation Mechanisms Yitayal Tebeje Department of Natural Resource Management, Debre Markos University P.O Box. 269, Ethiopia Abstract Global warming is among the greatest terrible horrors of the modern times. The global carbon cycle is taking place in three main reservoirs (the oceans, the atmosphere, and terrestrial systems), which store carbon in different forms and varying amounts. The forest ecosystems have large potential to act as a temporary and long-term carbon (C) pool. Global forest vegetation stores 283 Gt of carbon in its biomass, 38 Gt in dead wood and 317 Gt in soils (top 30 cm) and litter. Globally, the litter C pool accounts for an estimated 5% (43 Pg) of all forest ecosystem C stocks. Agroforestry practices can reduce or remove significant amounts of GHGs through increased carbon storage in biomass above-ground and below-ground and in soil organic carbon. Roots are an important part of the C balance, because they transfer large amounts of C into the soil. Grasslands, including rangelands, shrublands, pastureland, and cropland sown with pasture and fodder crops, covered approximately 3.5 billion ha in 2000, representing 26 percent of the world land area and 70 percent of the world agricultural area, and containing about 20 percent of the world’s soil carbon stocks. Soils are the largest carbon reservoirs of the terrestrial carbon cycle 1500–1550 Gt of organic soil carbon and soil inorganic C approximate 750 Gt both to 1 m depth. On a global scale, carbon loss from soils is mainly associated with soil degradation, including accelerated erosion and mineralization, and land use change, and has amounted to 78+/- 12 Gt since 1850. The idea of Reducing Emissions from Deforestation and forest Degradation (REDD) was conceived by United Nations Framework Convention on Climate Change (UNFCCC) as the main carbon emission reduction mechanism by developing countries. The implementation of improved land management practices to build up carbon stocks in terrestrial ecosystems is a proven technology for reducing the concentration of carbon dioxide (CO2) in the atmosphere – offsetting emissions from other sources and drawing down atmospheric CO2. Keywords: Carbon sequestration, Terrestrial carbon, Global warming and Carbon stocks. DOI: 10.7176/JEES/10-8-04 Publication date:August 31 st 2020 1. INTRODUCTION Carbon is present in the nonliving environment as carbon dioxide (CO2) gas in the atmosphere, as dissolved carbon in water (forming bicarbonate and carbonate solutions), and in carbonate rocks, coal, petroleum, natural gas, and dead organic matter (humus). It is found in the atmosphere primarily as CO2, CH4, and chlorofluorocarbons (Brown, S. and P. Leonard, 2004) Greenhouse gas emission is becoming a critical issue, as there is a growing awareness all over the world about its adverse impact and the consequent on climate change. At the dawn of third millennium, greenhouse gases are widely accepted by international scientific community as one of the potential threats to the existence of human kind coupled with extinction of other flora and fauna. The greenhouse gases with special optical properties that are responsible for climate warming include carbon dioxide (CO2), water vapors, Methane (CH4), Nitrous oxide (N2O), Nitrogen oxides (NOx), stratospheric ozone (O3), carbon monoxide (CO) and Chlorofluorocarbons (CFC’s). Among all these greenhouse gases, CO2 plays a leading role as it contributes to 50% of the total greenhouse effect (Bhardwaj SD, Panwar P, 2003). According to IPCC (2001) report, since 1800 the concentrations of CO2 in the Earth’s atmosphere have increased from around 280 parts per million (ppm) (by volume) to a current value close to 370 ppm. The increase coincides with the industrialization of human society and there is good evidence to show that it is caused by emissions of CO2 arising from human activities. The most important contributor to the recent increase in the global stock of atmospheric CO2 is the burning of fossil fuels (e.g. in power stations) and from the deforestation of land, particularly in the tropics. Carbon dioxide, along with a number of other gases present at lower concentrations (so called ‘trace gases’ such as methane (CH4) and nitrous oxide (N2O)), traps thermal radiation emitted from the Earth’s surface and so gives rise to warming of the Earth’s atmosphere. This warming (known as the ‘greenhouse effect’), enhanced by the accumulation of these gases particularly over the 19th and 20th centuries has led to a global mean increase in surface temperature of about 0.6 o C (IPCC, 2001). However, the challenges of climate change can be effectively overcome by the storage of carbon in terrestrial carbon sinks viz. plants, plant products and soils for longer periods of time. Richards JF and Flint EP, (1993) reported that, about 80% of the world’s potential for increasing Carbon storage in forests (estimated at 60-87 Pg Carbon from now up to 2050) lies in developing countries (Brown S, 1995). The forest woodland system sequestered more Carbon than all other categories collectively, but the