Tackling poverty by planting trees. Also aid in the Great Green Wall project of Africa, that is severely under funded.
For their Adopt a Sloth program - https://www.theslothinstitute.org/get-involved/adopt-a-sloth/
One Tree Planted Inc
1$ = 1 Tree planted
International Institute for Sustainable Development
Community Carbon Trees- Costa RIca
Planting trees, along with empowering communities
Akshaya Patra Foundation
Mid day meal programs for school children in India
World Wildlife Fund, Inc.
Advocacy and conservation
Rainforest Trust buys forest land and conserves it
Wildlife Warriors Ltd
Started by Steve and Terri Irwin, Australia Zoo Wildlife Warriors support the Australia zoo's animal hospital, among others