How does the enhancement of carbon sequestration by non-native forests affect other ecosystem services?

Abstract

Non-native trees (NNT) have been globally expanded to provide a variety of ecosystem services. Among these, the ability of forests dominated by NNT to remove atmospheric CO2 and mitigate global warming has garnered significant societal recognition in recent times. Non-native forests are often considered more efficient carbon sinks than native forests because of the typically fast-growing nature of NNT. Yet, NNT may have negative effects on other ecosystem services or biodiversity. We reviewed the literature searching for case studies simultaneously assessing effects of NNT forests on climate regulation – by means of carbon sequestration – and other ecosystem services or biodiversity. The carbon sink efficiency of forests was split into carbon flux and carbon stock in both aboveground and belowground compartments, considering that these components may respond in different directions to the introduction of NNT. While the body of research on individual ecosystem services or biodiversity is substantial, the number of studies addressing multiple services concurrently remains limited. Even so, we found a positive link between the effects of NNT forests on climate regulation, on soil fertility, and with weaker evidence, on erosion control. By contrast, effects of NNT forests on climate regulation showed a trade-off with water conservation in the ecosystem. This suggests that expanding NNT forests to promote the carbon sink function in water-limited areas is not an appropriate strategy to face global warming, as it could lead to decline the water supply for other functions.