Two symbols, one solution.
D000818:Animals; D001938:Brazil; D003247:Conservation of Natural Resources / Q000191:economics / Q000379:methods*; D017753:Ecosystem; D016468:Forestry / Q000191:economics / Q000379:methods; D017752:Greenhouse Effect; D014197:Trees / Q000502:physiology*; D014329:Tropical Climate; D001503:Ursidae / Q000502:physiology*