St. Louis Post-Dispatch: As atmospheric CO2 (carbon dioxide) levels continue to rise, enormous tree-planting campaigns are often touted among ways humans can try and limit climate change. In Africa, where some regions have been seen as ideal for this type of project, Guy Midgley has a message: Hang on. The botany and zoology professor at Stellenbosch University in South Africa explained that trees are already moving into African grasslands. Higher levels of carbon dioxide are beginning to change those ecosystems into...