You thought economics was contentious, dealing with people's wages and spending and retirement and taxes. So how does a melding of the environment on top of that notion work?
Environmental economics deals with how the economy intersects with the natural environment. Like use or extraction of natural resources (timber, oil, coal, etc.) or how the economic output impacts the environment (pollution, trash, and so forth).
Big, fat, hairy topic in the realm of the whole Global Warming discussion. See: Negative Externalities. With 7 (going on 15) billion people on this planet in 50-100 years, we have...challenges. And likely new beachfront property near Lake Tahoe.