Can tree planting alone lead to zero carbon emissions?

On June 5, World Environment Day, the Kerala Chief Minister assured that the Pachathuruthu government’s initiative will be the cornerstone of the state’s ambitious goal of achieving net zero carbon emissions.

The Pachathuruthu (green space/mini forest) project is an initiative to green barren lands by planting trees and indigenous plants. It focuses on creating natural biodiversity, including fruit trees, to absorb and store excess atmospheric carbon through the joint efforts of local government bodies and Mahatma Gandhi National Rural Employment Guarantee Scheme. The project, initiated on June 5, 2019 at Vengode in Pothencode panchayat, Thiruvananthapuram district, has grown from a modest plot of land worth six cents to 856.23 acres in five years.

A critical review raises serious concerns about its overall impact and feasibility in offsetting Kerala’s carbon emissions, making it net zero. It is reported that Haritha Kerala Mission aims to develop 1000 Pachathuruthus across the state, claiming that Kerala will achieve carbon neutrality by 2050, solely through tree planting. This claim is completely unrealistic.

Energy and carbon dioxide emissions

Kerala’s final energy consumption in 2022-23 was 1.4 billion tonnes of oil equivalent, resulting in 3.5 billion tonnes of CO2 emissions.

This consumption includes various energy sources, including electricity, coal, and petroleum products such as LPG, diesel, jet turbine fuel, and heating oil. Petroleum products account for the largest share, 64 percent, followed by electricity, coal, and gas.

During the same period, electricity consumption was 24,923 gigawatt-hours, equivalent to 1.87 billion tons of CO2 emissions. This is primarily because 70 percent of the state’s electricity needs are imported and generated primarily from fossil fuels. (Source: KSEB, enerdata.net and CII Data)

Tree planting and carbon sequestration

To offset its projected emissions of 3.62 billion tonnes of CO2 for 2023-24 through tree planting, Kerala would need to plant at least six billion trees, which would require 55 million acres of land (or five times the state’s geographical area). This is an impossible task, considering that the total land available for non-agricultural use, land under mixed crops, wetlands and community forestry is less than 1.16 million acres.

The recommended spacing for agroforestry systems is 20 feet x 20 feet, which allows for 109 plants per acre, as they need sunlight, water, and nutrients from the soil. Young trees absorb about 5.9 kilograms of CO2 per year, and mature trees can absorb about 22 kg per year.

We also need to consider that when trees die, the carbon stored in their biomass is released back into the atmosphere through decomposition, combustion (in the case of forest fires) or harvesting. However, soil can continue to store carbon long after the trees have died, contributing to long-term sequestration, provided the trees or leaves are not burned.

In addition, not all regions are suitable for large-scale tree planting due to potential negative impacts, such as loss of native species. Ensuring the survival and growth of planted trees over time requires proper species selection, effective planting methods, and ongoing maintenance.

Better options

The Draft Kerala Blueprint, prepared by the Confederation of Indian Industry with support from the Kerala Energy Management Centre, under an initiative of the Bureau of Energy Efficiency, indicates a potential reduction of CO2 emissions by 470 million tonnes per annum by 2031 through various energy efficiency initiatives at an estimated capital expenditure of Rs 4,453 crores.

Considering the growth observed in the Pachathuruthu project, which has expanded to 856 acres in five years, it is projected that the current project could cover a maximum of 5,000 acres by 2050. The estimated annual absorption of CO2 by 2050 through the Pachathuruthu project is between 12,000 and 20,000 tonnes, assuming that trees are planted on 5,000 acres and mature to absorb CO2 at the rate of 22 kg per year. Therefore, it is obvious that reducing the carbon footprint of the power sector should be a primary focus.

Greenhouse gas emissions, not just CO2

Achieving net-zero emissions requires more than just carbon dioxide (CO2) sequestration; it requires addressing the various greenhouse gases (GHGs) that contribute to global warming. While CO2 is the most abundant and persistent greenhouse gas, methane has a much higher global warming potential, being 28-34 times more potent than CO2 over a 100-year period. Major sources of methane include cattle, rice paddies, landfills, and reservoirs associated with hydropower plants and dams. Ignoring these sources in a carbon neutrality strategy undermines the credibility of the goal.

The Pachathuruthu project in Kerala, though praised as a positive initiative, cannot single-handedly take the state to net zero carbon emissions. The claim that this project will make Kerala a net zero state (100 percent offset) when in reality it will not offset even 1 percent is completely misleading. Improving energy efficiency is the most important action that needs to be initiated and prioritized to move towards net zero emissions.

Realistic, differentiated strategies across all GHGs and robust policy interventions are essential. Tree planting is part of the solution, but it must be integrated with broader, systemic changes to achieve lasting environmental impact. Government should initiate action to assess current emissions in each sector and monitor changes to this baseline each year, rather than making lofty claims of “net zero” emissions without proper scientific assessment.

C Jayaraman is a recipient of Fulbright Nehru Environmental Leadership and Fulbright Kalam Climate Change Fellowships, has a Ph.D. in Energy Management, and is currently the Managing Director of EQUINOCT Community Sourced Modeling Solutions, a technology startup.

The views expressed are those of the author and do not necessarily reflect his views. Down to the ground.