ответить на вопрос: what do you think is the biggest threat to our environment and why?

I think the biggest threat to people and life on Earth in general nowadays is global warming. Doubtless, when we burn petrol, oil and coal, lots of carbon dioxide is added to the atmosphere that upsets the Earth's heat balance. If we keep emitting current greenhouse gas, climate change will cause about a third of the planet's animals and plants to face extinction by the middle of the century.