There was a study made in a UK forest in where it was calculated the population of red squirrels and grey squirrels. There was a clear competition and by the end of the study, there were only grey squirrels. How the decline of the red squirrel population might affect its native ecosystem??

i think it is dna, i'm not totally sure but i think it might be.

they had the law tat factories that produces smoke cannot be built near residential buildings.

building of proper sewage system was done to ensure that the waste is carried away from the humans so that they do not get diseases from it.

also they built water systems to provide water in those areas which are drought prone.