Answer:
Global Warming
Step-by-step explanation:
The biggest concern for environmental scientists is Global Warming. Our Earth is getting warmer which is having drastic effects on our planet. Such effects include increased natural fires, decreased water supply, decreased farm yields, increased floodings, etc. Global Warming poses a huge threat to humanity and it is because of humanity's constant and ever growing usage of fossil fuels that Global Warming is becoming such a threat. This is what environmental scientists are mainly focused on.