why managing human resources is so important?

Answer 1

You mean for environment or for business?
As your question is in the category of environment&ecology, i assume that the former.
So, first, human resources management is responsible for finding the best performers for responsible, decision-making positions of people who would decide how to act towards a certain environment (whether to build up a dam or a national park on a certain territory).
Second, human resources management is important for hiring responsible and/or creative specialists (engineers and scientists) that can:
1) invent and implement environmentally-friendly production and materials;
2) make every-day job with all the responsibility and attention (Chernobyl explosion is the result of lack of responsibility):
3) effectively remove existing negative changes in environment.

Answer 2

To have a renewable resources and be it protected from over harvesting.