People in developed countries tend to have a larger ecological footprint then people in developing countries

That they do. From things like vehicles, to factory production and output of smog, to more need for resources such as trees and coal and oil. They have more and want more which affects the ecosystem way more than countries still trying to find their footing.

9.9 years

a = p(1 + rt) . . account balance after time t at rate r starting with principal p

3000 = 2500(1 + 0.0202t) . . filling in the given numbers

1.2 = 1 + 0.0202t . . divide by 2500

0.2 = 0.0202t . . . subtract 1

0.2/0.0202 = t ≈ 9.901

it will take about 9.9 years for the account balance to reach $3000.