The impacts of climate change are most strongly felt by subsistence farmers who are seeking to mitigate these effects by planting trees. This project aims to combine satellite measurements with social data on activity and participation. It aims to develop improved and transparent metrics for assessing the impacts of tree planting and strategies for expansion.
Explaining the science
The project uses the cloud based Google Earth Engine which allows anyone to access and analyse a catalogue of satellite imagery and geospatial datasets. This project is mainly interested in indicators of plant productivity and drought, for example NDVI, which measure the amount of chlorophyll in an image, or NDWI, which measures plant water content and serves as a proxy for plant water stress.
The specific satellite data being used comes from LandSat which gives a low-resolution but long-term survey of the areas of interest (primarily East Africa) and Sentinel which gives high-resolution (up to 10m) images for directly studying individual farms.
By combining these indices together with the very detailed organisational data of the project's partners at TIST (The International Small Group and Tree Planting Program), it's possible to calibrate models that infer tree cover from satellite images, as well as study landscape-scale changes occurring due to TIST and Kenyan NRT (Northern Rangelands Trust) conservation practices over their histories.
This analysis can also be combined with forest cover change datasets to understand any secondary effects of TIST's activities on the landscape, such as increases in forest cover near to TIST groves.
The high temporal resolution of the satellite data will allow the development of novel tools for assessing the impacts of tree planting and conservation farming, using indicators of plant productivity, vegetation structure and drought indices. These computational methods potentially provide cheap and effective ways to monitor progress in tree growth, resilience, conservation, SDGs as well as enhancing field surveys and land management.
The project partners at TIST will occasionally seed an area by bringing existing members to speak with locals about the benefits of the program. Past experience suggests that the gender balance of these meetings has a significant impact on their outcome. This work aims to identify significant social and environmental factors affecting the success of these seeds.
Improved and transparent metrics for assessing the impacts of their activities will be of direct value to tree planting and conservation organisations, supporting their growth and making the benefits of participation clear to members and funders. For example, the project is looking at areas managed by the Kenyan Northern Rangelands Trust (NRT) an association of community conservancies. An understanding of how and where community grazing plans are impacting grassland resilience will be invaluable to NRT, and will help communities to develop sustainable and drought-resilient grazing practices.
The International Small-Group and Tree Planting Program (TIST), a farmer led tree planting scheme are the main partners in this work. Their members are concerned about drought and soil erosion, so an increased understanding of the impact of TIST's tree planting will be invaluable in retaining members and growing the organisation. An understanding of the social factors at play in TIST: for example how information spreads, how the gender make-up of the groups affects their success, how the organisation grows, will likewise be invaluable and give important lessons for the future of both TIST and similar schemes in other countries.