The earth is a delicate balance, and that balance has to be kept if we wish to maintain a safe and healthy environment for human flourishing. Scientists have identified ten quantifiable boundaries that we should be observing, making it possible to chart our current performance.
As the graphic shows, levels of fresh water use, ocean acidification and so on are all currently within the green safety zone. There are places where these are serious problems, but taking the planet as whole, we’re within the limits. Not so with species loss. The margin of safety is 10 extinctions per million per year, and we’re heading towards ten times that. The limit you may be most familiar with is the CO2 limit of 350 ppm, the subject of much climate campaigning. Less familiar the nitrogen cycle. This is also out of balance, as we remove 120 million tonnes of nitrogen from the air a year and put it back into the world as fertilisers. The rush of chemical nutrients from agricultural land into water sources chokes out all animal life and eventually plants too.
You can read all the detail around this original way of describing our relationship with the environment in this feature in the Nature journal.