ACROSS
Greenhouse Gases (10 + 5 letters)
Deforestation (13 letters)
Landfill (8 letters)
Climate Change (7 + 6 letters)
Microplastics (13 letters)
Environment (11 letters)
DOWN
Atmosphere (10 letters)
Fossil Fuels (6 + 5 letters)
(9 letters) Solar Power (5 + 5 letters)
Global Warming (6 + 7 letters)
Recycling (9 letters)
The unscrambled word is "pollution".
Clue:
The release of harmful substances into the environment, causing damage and degradation.