About planetary challenges.

Douglas Fischer/EHS

A framework for assessing the scope and scale of human activity

In 2009, 28 leading scientists from around the world suggested a new way of looking at the scale and scope of human activities on this planet. 

"The Earth has entered a new epoch, the Anthropocene, where humans constitute the dominant driver of change to the Earth System," they declared. "Here we present a novel concept, planetary boundaries, for estimating a safe operating space for humanity with respect to the functioning of the Earth System."

That initial paper, published in the journal Ecology and Society, presented a preliminary assessment of key Earth systems influencing planetary health – climate change, biodiversity, global freshwater use, chemical pollution. For each process the scientists, drawn from institutions and fields across the globe, identified boundaries that, as they noted, "should not be transgressed if we are to avoid unacceptable global environmental change."

Almost a decade later, that work remains even more relevant. The 2009 framework was updated in a 2015 paper published in the journal Science

In that update, scientists concluded we've already passed four important boundaries.

One example: Nitrogen plays a crucial role in agriculture, and our ability to manipulate and harness it has allowed society to feed 7 billion. But nitrogen washing off our fields has a host of cascading effects, from impaired human health to the spreading dead zone in the Gulf of Mexico. 

Sofianne Finch/flickr

In the updated framework, scientists suggest a global production rate between 62 million tons and 82 million tons of nitrogen per year represents a safe operating zone for the environment.

Global production today is around 150 million tons.


It's worth noting the boundaries are not hard-and-fast edges, like a cliff. Rather, they should be seen as zones. 

Environmental conditions have remained remarkably stable over the past 10,000 years – coinciding with the rise of human civilization. But major changes in those conditions, whether natural or human caused, could endanger that equilibrium, with unknown but likely nasty consequences.

For climate change, atmospheric carbon dioxide concentration is the primary yardstick. That level remained remarkably stable at 285 parts per million for thousands of years before the industrial revolution. Since 1850, accelerating fossil fuel use and deforestation has pushed CO2 levels above 400 ppm. Scientists see a "zone of uncertainty" between 350 and 450 ppm. With atmospheric CO2 levels climbing 2 ppm per year, society will be in the "high risk" zone in a few decades.

Other areas where human activity has pushed natural systems beyond both "safe" and "uncertain" zones and into "high risk" are extinction rates, ocean acidification, and phosphorus production. The Washington Post in January published a graphic showing where scientists place us in each issue.

The framework makes clear two important challenges: 

  1. The stable functioning of the Earth system is a prerequisite for thriving societies around the world, and
  2. The Earth is an integrated system – i.e., the boundaries operate as an interdependent set of limits. 

The second point, authors of the 2015 paper note, has "profound implications" for our future, "because it emphasizes the need to address multiple interacting environmental processes simultaneously."

We can no longer, for instance, attempt to solve one problem – such as biodiversity – without considering other issues such as food production or climate change.

Equally important is the scale: So many of the problems, from ocean acidification to stratospheric ozone depletion, are global, while many of the drivers and solutions are local and regional. And the prospect of tighter resource constraints and rising environmental degradation sends this issue rippling into social equity and environmental justice arenas.


So what are the boundaries? The current framework sees nine:

  1. Climate change
  2. Change in biosphere integrity (biodiversity loss and species extinction)
  3. Stratospheric ozone depletion
  4. Ocean acidification
  5. Biogeochemical flows (phosphorus and nitrogen cycles)
  6. Land-system change (for example deforestation)
  7. Freshwater use
  8. Atmospheric aerosol loading (microscopic particles in the atmosphere that affect climate and living organisms)
  9. Introduction of novel entities (e.g. organic pollutants, radioactive materials, nanomaterials, and micro-plastics).

Some are well defined. We're well into the red, scientists fear, on genetic diversity loss and disruption to the earth's phosphorus and nitrogen cycles. On climate change and land-system change, we're in the yellow – the zone of "increasing risk." 

But others are so unknown and new that scientists can't or won't hazard an educated guess. "Novel entities" – the impact of contamination from our everyday consumer lifestyle, something we cover heavily at EHN.org – remains an unknown, as does atmospheric aerosol loading and the functional diversity of the biosphere.

Is there any good news here?

Yes: Many groups, seeing the science, are working on a unified approach to sustainability and growth. 

The Millennium Alliance for Humanity and the Biosphere, based out of Stanford University, is connecting activists, scientists, humanists and civil society to foster change.

Just across the San Francisco Bay, at the University of California, Berkeley, the Energy and Resources Group represents an interdisciplinary group of 100 faculty working on a sustainable environment and just society.

As science behind this complex interaction develops, the framework "provides us with a great opportunity to turn things around," say experts at the Stockholm Resilience Center.

"The planetary boundaries approach can be used as a framework for sectors of societies to reduce risk while developing sustainably," writes Johan Rockström, the Center's director. "This could create the conditions for long-term human prosperity."

At Environmental Health News, we are attempting to connect these dots—highlighting the planetary boundary framework as it manifests in environmental news stories from around the world.