Final answer:
Leach and Fairhead found that human interaction with the environment, specifically through soil fertility management and controlled fire use, actually increased forest cover over time rather than decreasing it, as was commonly believed.
Step-by-step explanation:
Research by Leach and Fairhead showed that contrary to the common belief that local people were contributing to the destruction of forest cover, human interactions had actually led to an increase in forest cover over time. Their studies in the forest-savanna transition zone of Guinea revealed that local land use practices, such as managing soil fertility and controlled use of fire for vegetation management, encouraged the development of forest patches. These patches were not only increased over time but also dynamically managed by the local communities for various purposes, from village protection to timber logging, which in turn enhanced the landscape's ecological richness.
Fairhead and Leach advocate for the use of mixed historical and satellite data to accurately capture the actual effects of local land use on forest cover. These findings highlight the importance of incorporating local knowledge and practices in conservation policies and challenge the perception that locals are always the culprits of deforestation.