He said the recent U.S.- China climate change pact was groundbreaking. Under the deal, the United States has set an emissions-cut target of up to 28 percent below 2005 levels by 2025 and China has vowed to cap growing carbon emissions by 2030.

"It is very significant, and a symbolic milestone has been made. It shifts the ground for the rest of the world and has significant impact," Steiner said.

Steiner said the collective environmental security of the world is also a matter of finance.

"Most obvious is the public finance needed to safeguard our environmental commons--from the water we drink and the air we breathe to the stewardship of vulnerable biodiversity essential to our circular economy, such as the endangered bee population whose pollinating activities are so vital to food production," Steiner said.

He said climate is another case in point, with the ongoing international negotiations placing considerable emphasis on the question of how much developed countries will finance developing countries'efforts to reduce carbon emissions, and the costs of communities'and economies' adaptation to climate change.

"The G20's focus this year on the challenge of financing long- term infrastructure needs of an estimated 5 trillion U.S. dollars annually worldwide has profound environmental dimensions," he said.

"Building energy efficient and climate resilient cities will be a defining feature of their future utility, both to their residents and to the global community."

Steiner said investing in agricultural systems that can remain productive in the face of changing and increasingly volatile weather patterns will be the basis for securing adequate, affordable, healthy food for tomorrow's growing global population.

"Environment is not just a matter for environmental ministers and policies," he said.