Take a look at these facts: between 1930 and 2000 global production of man-made chemicals increased from 1 million to 400 million tonnes each year. The amount of pesticide sprayed on crops has increased 26 times in the last 50 years.
The impacts are enormous and widespread (and this is an understatement).
Not too scared to find out more on this incredible own-goal? Here's some interesting reading.
> Next in at number 2 we have invasive species