The air is full of carbon dioxide and other pollutants;
The ocean is emptying;
We have observed record setting harvests over the last few years, and yet chronic hunger persists and has recently been increasing;
The planet is experiencing the 6th great extinction;

All of these are the result of human activity.

This evidence illustrates that we have not responsibly managed, neither through governance nor technology, our environmental resources. In the absence of finding a sustainable relationship with our ecosystem, we might conclude that we have reached Earth's carrying capacity.

The 6th Extinction
A mass extinction is under way. Human activity, not natural phenomenon, is the difference between this extinction and the five previous big extinctions that have occurred in Earth's history. The current extinction is driven by habitat loss, overexploitation of species, invasive species and pollution. All of these, the result of humans.

The current extinction rate is between 1,000 and 10,000 times higher than the natural rate. (International Union for Conservation of Nature, IUCN) Current estimates put the extinction rate at roughly 30,000 species per year which is about three per hour. By the end of this century, about half of Earth's plant species could be gone. (Pitman and Jorgensen, 2002) For an assessment of global biodiversity, refer to the IUCN Red List.

The size and scope of actions necessary to address climate change can cause paralysis and inaction. In the absence of public policy, emissions would grow to around 60 billion metric tons of carbon dioxide by the middle of this century from current emissions of roughly 30 billion metric tons per year. In order to achieve climate stabilization, most analysis recommends an emission reduction target of 50% to 100% by 2050 from today's levels. Politically, there has been progress. The United States House of Representatives recently passed the climate and energy bill, known as the American Clean Energy and Security Act. The incredible difference between the do-nothing, status quo trajectory and these targets can be daunting. This month on EarthTrends we will give an overview of the most commonly discussed technologies and practices that get us from here to there as well as a consideration of the associated costs of implementing these solutions.

Twenty-two years ago, the Montreal Protocol was adopted to protect the ozone layer from depletion. It was the first-ever international agreement on the regulation of chemical pollutants. (Carlowicz, 2009)

The Montreal Protocol was characterized by Kofi Annan as "one of the great success stories of international cooperation." As a recently released simulation of Earth without the Montreal Protocol shows, there would have been grim consequences for a business as usual approach. (See Figure 1.) Among other things, this simulation predicts an Earth with a dangerously insufficient ozone layer by 2050.