The Contribution of Trees Outside of Forests to Landscape Carbon and Climate Change Mitigation in West Africa

Abstract

While closed canopy forests have been an important focal point for land cover change monitoring and climate change mitigation, less consideration has been given to methods for large scale measurements of trees outside of forests. Trees outside of forests are an important but often overlooked natural resource throughout sub-Saharan Africa, providing benefits for livelihoods as well as climate change mitigation and adaptation. In this study, the development of an individual tree cover map using very high-resolution remote sensing and a comparison with a new automated machine learning mapping product revealed an important contribution of trees outside of forests to landscape tree cover and carbon stocks in a region where trees outside of forests are important components of livelihood systems. Here, we test and demonstrate the use of allometric scaling from remote sensing crown area to provide estimates of landscape-scale carbon stocks. Prominent biomass and carbon maps from global-scale remote sensing greatly underestimate the “invisible” carbon in these sparse tree-based systems. The measurement of tree cover and carbon in these landscapes has important application in climate change mitigation and adaptation policies.

Sub-continental-scale carbon stocks of individual trees in African drylands

“…Reaching this level of detail is critical for dryland monitoring and management because dryland trees grow isolated and in highly variable size and density. Most current studies producing or using areal averages of tree cover, wood mass or carbon stocks in drylands are either at the very local level 12 or the information for drylands is derived from global maps 13 , which are rarely trained and validated in drylands and often apply the same method on both forests and dryland vegetation 6 – 8 . Although national tree inventories exist for few dryland countries, the amount of labour required and their uncertainty are high.…”

Nation-wide mapping of tree-level aboveground carbon stocks in Rwanda

“…Also, previous work has overestimated the extent of forests by the inclusion of shrubs and bushes as forestland 47 . Uncertainties in tree cover estimates propagate to estimations of carbon stocks, resulting in large uncertainties in biomass and carbon estimates and maps 48 (Extended Data Fig. 4 and Extended Data Table 1b ).…”

Leveraging the Power of Forests and Trees for Transformational Adaptation

“…The real potential of forests to facilitate both mitigation and adaptation, however, is still largely untapped. This is even less tangible when it comes to trees outside forest and agroforestry systems (Mbow et al 2014, Skole et al 2021Somarriba et al 2021;van Noordwijk et al 2021, Park et al 2022. This paper aims to summarise a set of clear and tangible key principles, which are backed by science, to fully tap into the potential of forests and trees for adaptation.…”