Review on environmental impacts of forest carbon offset projects and potential assessment methodology on non-carbon ecosystem attributes

Abstract

Facing the current climate crisis, forest carbon offset projects have gained attention due to the strong carbon sequestration capacity of forests and have been widely applied globally. The carbon credits generated by these projects can be traded on the carbon market, which allows emitters to reduce their net emission by buying these credits. These projects are also claimed to have co-benefits on other ecosystem services such as biodiversity, water and soil conservation, which are closely related to composition, structure and function of the ecosystem. However, more doubts about the effectiveness of these projects have been raised recently, which requires closer examination of the ex-post environmental impacts of these projects. Moreover, there is a lack of impact methodology used to assess non-carbon environmental impacts in the project protocols, making the impact assessment of non-carbon attributes difficult and thus usually overlooked. This article aims to answer two questions through literature review: What are the ex-post environmental impacts of forest carbon offset projects? What are the potential impact methodologies that could be integrated into FRR projects under carbon market mechanism to assess non-carbon environmental effects? The results showed an overestimation of carbon sequestration and climate mitigation effect of forest carbon offset projects and the lack of systematically designed assessment studies in non-carbon environmental impacts. Thus, we know very little about the environmental impacts of these projects apart from the carbon aspect. This further proves the current need of developing protocols to assess non-carbon ecosystem attributes. The review of the second question gave an overview of the currently available indicators and methods used to assess forest restoration success as potential options of choice. Although the development of the indicators is relatively mature, traditional sampling methods are time-consuming and expensive, making it difficult to apply to large scale projects and remote sensing technology cannot guarantee the measurement of some important indicators. To conclude, there is an overestimation of climate mitigation effects of forest carbon offset projects and we know little about the non-carbon environmental impacts of these projects. Measures are needed to improve the performance of these projects in climate mitigation and studies are needed in finding more cost-effective sampling methodology for different non-carbon indicators. More attention should also be paid to incentivize the evaluation of non-carbon ecosystem attributes, which is crucial in accelerating the development of relevant protocols.