WCS High Integrity Forest (HIFOR) Investment Initiative: The Science Basis
WCS Forests and Climate Change Program
This brief describes the science basis for the High Integrity Forest (HIFOR) Investment Initiative. The initiative aims to create a new climate and biodiversity asset class to help finance the protection of high integrity tropical forests — those that are least degraded by human impacts — on the basis of their role in climate change mitigation and biodiversity conservation. The HIFOR Unit represents a hectare of well-conserved, high integrity tropical forest. Associated with this unit are metrics that quantify climate regulation benefits (in terms of the number of tons of net CO2 removals into forest biomass over the course of a decade) and biodiversity conservation benefits (in terms of the number of hectares of high biodiversity forest maintained with high integrity over a decade). Large, remote, high integrity forests, and hence the services they provide, are often wrongly perceived to be safe from human pressures, but in fact face substantial and growing risks, and so their protection represents a critical conservation priority. For example, from 2017 to 2021 the extent of high integrity tropical forest declined by about 3.1% per year. Infrastructure expansion, logging, agriculture, fires, mining, and hunting all drive this trend. Natural ecosystems worldwide, primarily forests, reduce the impact of anthropogenic GHG emissions by absorbing ~30% of anthropogenic CO2 emissions. Carbon uptake by this “land sink” is distinct from the uptake associated with forest restoration, which is accounted for as part of “net land use change.” The action of this sink (currently 11.4 GtCO2 per year; 765 GtCO2 since 1850) has probably prevented around 0.6°C of global warming. Tropical forests mapped as ‘high integrity’ likely contribute around 1.8 GtCO2 per year to the land sink. The strongest average removals in high integrity tropical forests are found in Africa (2.9 tCO2 ha-1 yr-1), followed by Asia (2.0 tCO2 ha-1 yr-1) and the Americas (1.1 tCO2 ha-1 yr-1). Deforestation and degradation are eroding the area that contributes to the sink, whilst climate change and other factors are slowing the rate of carbon removals in some remaining areas. Loss or degradation of high integrity forest cover in the tropics typically causes additional climate warming, quite apart from the carbon impacts, by altering land surface energy and moisture exchanges. These biophysical processes increase the estimated warming effect of tropical deforestation or degradation by about half compared to counting only CO2 emissions. Total deforestation in the tropics could increase global warming by around 0.28°C (at least 0.11°C of this from high integrity forests) through biophysical effects alone. These biophysical effects also promote local climate stability, lowering average peak temperatures in nearby areas by around 1.0°C (range 0.2-2.4°C depending on locality) and reducing extreme temperatures by substantially more. Higher ecological integrity correlates with higher biodiversity. High integrity forests support consistently higher numbers of forest-dependent species, ensure lower extinction risk for the species present, support higher genetic diversity within species and lead to a lower risk of ecosystem collapse. Loss of integrity has an impact on the many functions (often called services) an ecosystem performs. High integrity forests are also better able to cope with climate change and other stresses. In addition to the climate regulatory functions and biodiversity values that this brief focuses on, high integrity forests embed many other environmental values, including large carbon stocks, regulation of local and regional hydrology, decreased risk of zoonotic disease spillovers, and contributions to the livelihoods and cultures of Indigenous Peoples and other local communities. High integrity forests have long helped to buffer us against the worst effects of climate and biodiversity crises. If we are to meet the 1.5-degree goal, halt human-caused extinctions and prevent the collapse of many ecosystems, it is essential that we invest in their protection.

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