What impacts the world environment?

Impact is a broad word in itself. Human activity on the face of the earth causes some impact or the other. In prehistoric times, when humans first tilled the land and made use of resources to develop tools for their survival, the effect of their actions in the form of depletion of the resources was negligible. Now with fast growing populations and complexities of the tasks at hand, it becomes multiplied. Impact on the world environment include resources available to sustain life, climate change, survival of species and quality of life on our planet. It is dependent on three main factors; Population, Consumption Patterns and Technology. If these variables are expressed as,

 I= Impact of a certain program or action on the concerned environment
P= Population in that area
A= Consumption patterns of population
T= Level of Technology used for the action per unit population,

then they are expresses as this relationship,

I=PxAxT   which shows that the variables are directly related to the impact. 

See this explanation by Prof. Jonathan Tomkin of University of Illinois at Urbana Champaign

http://spark-public.s3.amazonaws.com/sustain/low-res_videos/CSRA-V-2012-1-W1-M2_CSRA.mp4