Introduction

Carbon constitutes the fundamental element in the earth system including the food chain of biota and exists in different forms and reservoirs, which are distributed and continually exchanged among the atmosphere, biosphere, lithosphere, and hydro- sphere. Autotrophic organisms uptake carbon dioxide (CO₂) during photosynthesis transforming the energy from the sun into a chemical carbohydrate molecule, converting carbon in the atmosphere to fuel and structural materials for living organisms. Rampant deforestation and fossil fuel burning have been adding to the global carbon dynamics with the transformation of inactive carbon. The activities include burning of fossil fuel (transportation, power generation), industry, agricul- ture, polluting streams as well as water bodies and unplanned urbanization. Postin- dustrialization era witnessed an increase in GHG footprint, which constitutes 72% of CO₂. The escalation in human-induced greenhouse gas (GHG) emissions has been witnessed as 400 ppm (parts per million) from 280 ppm CO₂ emissions as compared with preindustrial era, which has contributed to the global warming [5] with changes in the climate, which affected people’s livelihood with the erosion of key ecosystem services including ecosystem productivity, water holding capacity, etc.

Forest ecosystems are the large repositories of terrestrial carbon and play a crucial role in the carbon cycle (C-cycle) through sequestration of atmospheric carbon in the above ground biomass (AGB), below ground biomass (BGB), and soil organic carbon (SOC). Forest and soil ecosystems’ role in maintaining the carbon balance is evident from the uptake of 30% (2 Pg (petagrams) of the annual anthropogenic CO₂ emissions. The forests storing large quantities of carbon per unit area packed down through photosynthesis, which gets released with the mismanagement of fragile ecosystems due to unplanned developmental activities with anthropogenic pressures [52]. The annual carbon sequestration by the world’s forests has been estimated as

2.4 Gigaton C [34]. Soil stores about two to three times more carbon in organic form apart from forest woody biomass [56]. Carbon stored in soils as soil organic carbon (SOC) and the studies focusing on soil’s potential in sequestering carbon is scanty and received relatively limited attention from the policy community, compared with carbon storage in the above ground wood biomass [3, 24, 56]. SOC constitutes the largest terrestrial carbon pool with an estimate of 700–3000 PgC (1 PgC 1*10¹⁵gC) across the globe [6]. SOC content in the soils varies based on climate, moisture, physiography, soil type, elevation, terrestrial vegetation type, density, and extent. However, inappropriate land-use changes with mismanagement, soil becomes a source of greenhouse gas emissions (CO₂, CH₄). This necessitates prudent land management in agricultural practices, restoration of eroded and degraded forest soils to improve soil carbon pool [25]. The C pool in the topsoil is about 2011 PgC

[33] accounting to 4.1 times of the biotic pool, and three times of the carbon in the atmosphere. Soil Organic Carbon (SOC) in the top 50 cm soil depth in India is estimated to be about 92.1 tons per ha in littoral swamp and 37.5 tons per hectare in tropical dry deciduous forests [6]. The total SOC in Indian forests accounts to 4.13 PgC (top 50 cm soil depth) and 6.81 PgC (top 1 m), which highlights the need for protection of soil with the appropriate conservation strategies to mitigate greenhouse gas emissions and associated climate changes.

Burning of fossil fuel [30], escalated industrial activities [29], higher deforestation [4], and land degradation [41] highlight the extent of anthropogenic-induced global warming. This unrestrained increase in global atmospheric carbon since the dawn of industrial revolution and implications changes in the climate on water and food security has driven the attention of policy-makers across the globe to focus on the earth’s carbon stocks and flows. Large-scale land-use land cover changes (LULC) altering the integrity of forests, soil and aquatic ecosystems with the associated emissions have been contributing toward higher greenhouse gas (GHG) footprint. LULC changes have not only eroded the sequestration capability directly but also disturbed the amount of vegetation residues (organic matter) returned to the soil [36, 49]. LULC changes have been posing a greater threat by altering their potential of sequestration, escalating vegetation die-off, and increasing instances of wild- fire [13] and have contributed to about one-third of all anthropogenic carbon [19]. LULC change-induced deforestation resulting in 90% of net carbon emission across the globe and acting as a source of 20% annual greenhouse gas emissions into the atmosphere [33]. This has prioritized the need for understanding of LULC changes with the associated decline of biomass and carbon storage for framing international policy strategies to reduce greenhouse gas emissions by reducing the abrupt LULC changes. LULC changes and their impacts vary across the regions, which neces- sitates the regional-specific management [42] in contrast to the global policy and regulation. Agriculture, energy production, industrial activities, waste mismanage- ment, and transportation are the major carbon-emitting sectors to be accounted for carbon budgeting as mismanagement in these sectors have contributed to a higher quantum of greenhouse gas emissions [1, 2, 58, 63].

The systematic quantification of carbon stock with an assessment of GHG emis- sions from various sectors would aid in framing the land-use policies and curb the irrational carbon emission from abrupt LULC changes. The global CO₂ emission is quantified as 36,153 million tons, with countries such as China (27%), USA (15%), European Union (10%), and India (7%) accounts 58% of the total emissions [26]. The top 15 countries contribute 26,125 million tons and the rest of the world as 10,028 million tons. The top 15 countries contribute 72% of CO₂ emissions and 28% by the rest (of 180 countries). China alone accounts to produce on its own 28% of CO₂ emis- sions (9.8 billion tons), 18.8% of global methane emissions (1.7 billion tons CO₂e), and 18.4% of N₂O emissions (545 million tons CO₂e). Large-scale LULC changes leading to deforestation account for 8% of the global carbon emissions (4.9 billion tons per year in the tropical forests). This has been responsible for dynamics in carbon stocks with the lowered capability of carbon sequestration, which has prompted to

assess the extent and role of drivers of the carbon emissions to evolve strategies to mitigate changes in the climate. Advancements in Geoinformatics (GIS technolo- gies) and availability of the multi resolution temporal remote sensing data with field data have aided in the land-use land cover mapping, quantification of above ground biomass (AGB), below ground biomass (BGB), and soil carbon. The remote sensing with continuous data support has been useful in the quantification of carbon footprint through measurement of carbon stock and emissions, which vary with the climate, land-use practices, and changes in the land cover and land uses [7, 40]. The insights of carbon dynamics through quantification of carbon footprint and the extent of carbon removal by carbon sinks would help in evolving strategies and frame appropriate policies to mitigate carbon footprint and implement location-specific conservation measures.

Afforestation with the location-specific endemic species of vegetation, arresting deforestation process through the improved regulatory mechanisms, transition to the energy-efficient devices, and environmentally sound technologies are some of the potential approaches for sequestering carbon and mitigate carbon emissions. Plants (trees, grasses, herbs) take up atmospheric carbon dioxide during photosynthesis and stored as carbon in biomass (trunks, branches, foliage, roots) and soils. Storing carbon in forests or through plantations in the form of standing biomass consti- tutes a potential carbon capture and storage (CCS) option [32]. The global potential of carbon sequestration through plants was estimated as 5–15 Gt C/year, which depends on the land-use practices, climate, etc. [23]. REDD and REDD initiative (Reducing Emission from Deforestation and Degradation) developed by Parties to the United Nations Framework Convention on Climate Change (UNFCCC) is an efficient strategy to promote conservation while reducing greenhouse gas emissions due to deforestation and forest degradations (accounting to 11% of global carbon emissions). Mitigation of impacts of the changes in climate and stabilizing global average temperatures within two degrees Celsius entails reducing emissions from the forest sector, in addition to other sector mitigation actions. REDD creates a financial value for the carbon stored in forests by providing financial incentives to the developing countries to reduce emissions from forested lands and invest in low-carbon paths to sustainable development through increasing forest cover, less- ening nationwide deforestation rates, carbon emissions, and reducing degradation of various geographical regions [57]. The carbon credit payment scheme as per the Kyoto Protocol obligations is another initiative to curb the carbon and carbon seques- tration through effective management. The scheme allocated credits according to the actual amount of carbon sequestered by the trees as modest land based ($77.91 per hectare per year) and tree based ($0.2 per m³ per year) to minimize the abandonment or degradation of forests [18]. These international initiatives toward mitigation of carbon dioxide emissions through improved forestry activities necessitate the under- standing of spatial and temporal carbon dynamics. Objectives of the current research are (i) understanding spatial patterns of land-use dynamics in Karnataka State, India;

(ii) quantification of the carbon emissions; (iii) estimation of the carbon seques- tration potential of forests plants and soil; (iv) assessment of the impact of LULC changes on carbon sequestration potential; (v) likely scenario of carbon dynamics

with the current trends of changes and also likely changes due to the policy of large scale developmental projects; and (vi) suggestions towards reducing deforestation and land degradation.