Planting forests no panacea for the climate crisis: IPCC -Tarun Gopalakrishnan
-Down to Earth
The IPCC’s Special Report on Climate Change and Land says land-based carbon sinks are not limitless
The carbon cycle is classically described in terms of ‘sources’ and ‘sinks’ of emissions. The electricity sector, which converts fossil fuels into light and heat, is a source (as are most human activities since the dawn of the industrial age).
Identifying sinks is trickier. We know that, as a general principle, more forest cover equals more carbon sequestration (or sink) potential. It is much more difficult to put a number on how much carbon forests can absorb.
The special report on Climate Change and Land released on August 8, 2019, by the Intergovernmental Panel on Climate Change (IPCC) illustrates this difficulty. It thus delivers a wake-up call for policymakers — that aggressive forestry targets do not excuse cowardice in cutting emissions from fossil fuel use. To make this case, it explicitly identifies the limits of carbon sequestration by forests.
The report estimates the mitigation potential from reducing deforestation and forest degradation at between 0.4 and 5.8 gigatonnes of carbon dioxide per year. By comparison, the energy sector accounted for 33 gigatonnes of carbon dioxide in 2018; coal alone accounted for over 10 gigatonnes.
Headlines may continue to give the impression that planting forests is a panacea for the climate crisis, but scientists are much less sanguine in their projections.
The IPCC indicates that some land-based response options “take decades to deliver measurable results” because “adaptation and mitigation benefits from afforestation/reforestation depend on the growth rates of trees”.
Besides, afforestation, reforestation and agroforestry “do not continue to sequester carbon indefinitely” — eventually “the net annual removal of CO2 from the atmosphere declines towards zero”. The report also notes that any sequestration gains are “at risk from future loss (or sink reversal) triggered by disturbances such as flood, drought, fire, or pest outbreaks, or future poor management.”
The long view on forestry stands in contrast with the report’s statements on “Action in the near term”. This section of the report’s summary for policymakers makes clear that “the consequences of inaction on […] mitigating climate change exceed the costs of immediate action in many sectors.”
It also makes clear the consequences for not acting immediately, stating that “[d]eferral of Greenhouse Gas emission reductions from all sectors implies trade-offs including irrevocable loss in land ecosystem services required for food, health, habitable settlements and production, leading to significant economic damage to many countries in many regions of the world”. (emphasis ours)
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