Related by context. Frequent words. (Click for all words.) 71 ozone layer 52 biodiversity 52 coral reefs 51 ozone depletion 50 ozone depleting substances 50 ozone 48 acidification 48 Ozone 47 biosphere 47 bio diversity 47 marine ecosystems 46 CFCs 46 peatlands 46 Global warming 45 ecosystems 45 global warming 45 ocean acidification 45 Greenland ice 45 climate change 45 glaciers 45 marine ecosystem 44 oceans 44 polar ice 44 Greenhouse gases 44 polar regions 44 Antarctic ice 44 desertification 44 tropical rainforests 44 rainforests 44 coral bleaching 43 Amazon rainforest 43 ecological 43 carbon sinks 43 Environment Programme UNEP 43 tropical forests 43 melting glaciers 43 habitats 42 reefs 42 permafrost 42 ultraviolet rays 42 Montreal Protocol 42 mangrove forests 42 corals 42 freshwater 41 fragile ecosystem 41 depletion 41 atmospheric carbon dioxide 41 atmospheric CO2 41 acid rain 41 deforestation 41 soil erosion 41 humankind 41 planet 41 flora 41 UV rays 41 carbon dioxide CO2 40 boreal forest 40 bleaching 40 Carbon Dioxide 40 rainforest 40 environmental degradation 40 CO2 40 coral reef 40 ultraviolet radiation 40 Biodiversity 40 tropical rainforest 39 UNEP 39 species 39 tooth enamel 39 Arctic 39 tropical forest 39 mangroves 39 Global Warming 39 melting ice 39 forests 39 Antarctica 39 polar bears 39 wildlife habitats 39 coral 38 mangrove forest 38 humanity 38 habitat 38 anthropogenic 38 wetlands 38 carbon dioxide 38 Glaciers 38 manmade 38 Carbon dioxide 38 mankind 38 Environment Programme 38 fragile ecosystems 38 lichens 38 Arctic Ocean 38 ice melts 38 aerosols 38 lichen 38 Himalayan glaciers 37 UV radiation 37 Malnutrition 37 mass extinction 37 Antarctic