In 1896, Svante Arrhenius asked a very important question: why is the Earth a habitable temperature for humans and other forms of life? Why isn't it too cold? His answer of course was the "greenhouse effect" provided by natural levels of carbon dioxide in the atmosphere—280 parts per million. He even was able to calculate with pencil and paper what doubling that concentration would do to the planetary temperature and came remarkably close to what the supercomputer models project today. We are well on the way to a much hotter planet at 400 ppm today.
What Arrhenius could not have known was anything about the detailed history of the planet's temperature for the past hundreds of thousands of years and in particular that the last ten thousand years have been a period of unusual stability in the planet's temperature. Those are the conditions that nurtured the rise of human civilization. Indeed the entire human enterprise is based on the assumption of a stable climate. And in the same ten thousand years all ecosystems have been adjusting to a stable climate.
All of that is changing. The planet is currently 0.8 to 0.9 degrees warmer than in pre-industrial times and we continue to load more carbon into the atmosphere. The finger prints of climate change are everywhere in living systems, sea level rise and increasingly acid oceans.
That is not the only things we are doing to the living planet which is our home. This was most brilliantly and eloquently outlines in a paper on planetary boundaries in Science in January. Nitrogen use has doubled the amount of naturally available biologically active nitrogen. Aquatic dead zones proliferate. The Phosphorous cycle is also beyond the "safe zone."
Biodiversity loss is the most dramatic for the simple reason that all environmental problems affect living systems such that biodiversity loss integrates all environmental problems. Biodiversity loss as a measure for lowered carrying capacity of the planet is just one aspect of it, because in biodiversity is the potential to advance the life sciences in major way—e.g., a Nova Scotia soil fungus has recently been shown to have the key to blocking the mechanism super resistant bacteria ("super bugs") use to ward off the effects of antibiotics. Every species contains a unique set of solutions to a unique set of biological problems and opportunities. We ned to look at biodiversity as a living library for the life sciences and treat it with the same respect we accord our own libraries.
All the above means that science, mathematics and technology are important as they never have been before. But they will serve us best if we engage in them with a combination of curiosity and exploration combined with a sense of respect for the environment. This is not so much about limitations as it it about respect for the systems which supports us and brought us into being. Nature can in fact do a lot for us: restoring destroyed and degraded ecosystems can help avoid a full half of a degree of climate change while providing all kinds of additional benefits. And there is so much we can learn from the living library.
It is an exciting time. Scientists have begun to refer to the present as a new geologic era, the "Anthropocene" because the impact of humanity has become geological in scale. I for one will be far happier when it comes to mean that we have understood the limits as well as the biological potential, and have come to manage ourselves in ways that provide not only a sustainable future for humanity and other forms of life, but also one that recognizes the opportunity the life and other sciences can provide.
Dr. Thomas Lovejoy
George Mason University
Professor of Environmental Science & Policy