She’s using air quality sensors to measure how air pollution impacts disadvantaged people in the U.S. and sub-Saharan Africa.

In Sierra Leone, only 1 percent of rural citizens have access to electricity. Easy Solar, founded by graduates of Columbia’s School of International and Public Affairs, hopes to change that.

Earth Institute agricultural scientist Pedro A. Sanchez argues in a new essay that new developments in both science and politics give him hope that sub-Saharan Africa will be able to feed itself by 2050, even with a projected population by then of about 2 billion people.

Innovations in the 2014 EPI include a new wastewater treatment indicator; a new approach to climate change indicators; and two new satellite-derived indicators for air quality and forests.