Transgressing Planetary Boundaries

Are humans shifting the entire Earth system?

The diagram shows the nine planetary boundaries. Source: Steffen et al. (2015), Design: Globaia

Four out of nine Planetary Boundaries (PB), beyond which humanity runs the risk of major environmental crisis, have to date been transgressed. These include: genetic diversity, climate change, biogeochemical flows and land-system change. That is the message of a large group of scientists, lead by Will Steffen, who recently published their improved estimation in the journal Science

The concept planetary boundaries was first used in the original paper from 2009, in which Rockström et al. identified nine different natural processes that are critical for the stability of the Earth system. In that paper they also estimated boundaries, parameters of change, within which humanity would like to stay to ensure long term progress and survival.

By transgressing four out of nine boundaries humanity is now on the verge of shifting the entire Earth system, from a friend with predictable and temperate climate full of diversity to a foe with unpredictable and warmer climate with less diversity. For example, large marine ecosystems could change dramatically due to ocean acidification and eutrophication, higher temperatures could threaten agricultural productivity and human health, and continued loss of biodiversity could mean faster spread  of diseases and pests.

Steffen explains that once we have passed a threshold it becomes increasingly difficult to turn back or even slow down changes in the Earth system. In other words, it could potentially have catastrophic consequences. The authors have named two of the nine PBs "core" since they are fundamental to the integrity of the Earth system. These two include climate change and biosphere integrity, and we have basically passed both of those two boundaries.   

0 kommentarer:

Entering Earth's 6th Great Mass Extinction

The 6th Great Mass-Extinction

For a decade now it has been widely debated whether humanity has set in motion a sixth great mass extinction event, comparable to the catastrophe which erased the dinosaurs some 66 million years ago. According to a recent study by Ehrlich et al. (2015) there is no longer any doubt, we truly have.

There is general agreement among biologists that extinction rates have reached levels unparallelled since previous mass extinctions on Earth. However, some have believed the numbers to be overestimated. But this new study confirms that species are disappearing up to about 100 times faster than the normal rate between mass extinctions, known as the background rate. If allowed to continue, life would need millions of years to recover.

The study took a precautionary approach and only allowed for conservative estimates, which means that their calculation probably underestimate the severity of the extinction crisis.

As human population continues to grow and consumers become more affluent more and more natural habitats will be altered or destroyed. Already in 2005 scientists warned that about 60% of all ecosystem services had been degraded or destroyed (Millennium Ecosystem Assessmentt). The long list of impacts include: land clearing for farming, logging and settlement, invasive species, carbon emissions that drive climate change and ocean acidification and toxins that alter and poison ecosystems. 

While there is still much discussion about the causes of some mass extinctions, it is generally believed that they can occur when the biosphere is under long-term stress, for example from a warming climate generated by greenhouse gasses in the atmosphere. As ever more species face extinction we lose the vital ecosystem services they provide, such as: pollination, water purification, pest control, storm control, soil regeneration etc. For its continued existence mankind is reliant upon an untold number of species that maintains the function of those services. As these species disappear, that existence becomes increasingly fragile.

Stanford biologist Paul Ehrlich calls for fast action to conserve threatened species and habitat before the window of opportunity closes. Below is a video from Standford with Ehrlich describing the issue.

0 kommentarer: