standard Earth tipping points?

How do you identify tipping points before they occur?  This question is being asked by many scientists including those in the Tipping Points project about how early warning signals could be detected before a system – a biological, climate or even economic one – tips into an entirely different state.  Many researchers are concerned that the Earth itself will undergo a critical transition that will cause radical physical, ecological and social changes that are also difficult to anticipate.  One of the main drivers of this is climate change, but others are also included.  The world could likely experience unprecedented transformation on a number of different scales, but when this will occur is difficult to say.

It may already be happening as signs of the planet’s changing climate have indicated.  But have we passed a tipping point?  Are the changes inevitable and is there no turning back?  These two questions in particular have sparked a frenzy in the popular media.  A recent study published in Nature, ‘Approaching a state shift in Earth’s biosphere’, reviews research on different parts of the Earth’s biosphere providing context and useful knowledge for understanding the critical state of the planet at this time.

In the past, large-scale planetary shifts include the move from the last glacial to the present inter-glacial and the Cambrian explosion which led to an incredible increase in biodiversity with a plethora of plant and animal life.  What is important to keep in mind about these and other global-scale shifts is that they all occurred during ‘global scale forcings that modified the atmosphere, oceans and climate’.

These examples suggest that past global-scale state shifts required global-scale forcings, which in turn initiated lower-level state changes that local controls do not override. Thus, critical aspects of biological forecasting are to understand whether present global forcings are of a magnitude sufficient to trigger a global-scale critical transition, and to ascertain the extent of lower-level state changes that these global forcings have already caused or are likely to cause. ( ‘Approaching a state shift in Earth’s biosphere’ 486, 7401. Nature

Now we are witnessing the conditions for yet another large-scale global shift that may have already begun some time ago.  This is a most difficult situation to be in as there is also uncertainty as to how vast these changes will be and how long they will take to occur.  So what are the drivers that could lead to a planetary ‘tipping point’?  These are the main ones according to the review:

  • Human population growth and consumption of resources
  • Habitat transformation and fragmentation
  • Energy production and consumption
  • Climate change

Desertification, one of many environmental changes that threaten global agricultural productivity.

Each of these forcings are interrelated or connected in some way and all of them are related to human activities.  Population growth is an incredibly sensitive issue that is difficult to talk about directly from a political standpoint, but there is also the deeper question of how people live instead of focusing solely on how many.  If populations do not change their rates of consumption or destruction of habitats (instead of creating new ones) for example, then population itself is the culprit.  The same could be said for energy production and consumption which has inadvertently led to people at a global scale engineering the planet’s climate (see Air pollution, geoengineering and climate change) – if the means change then maybe the problem can be resolved.  I think there is a strong argument for looking at the ways people live as the main reason for many of the global problems the world’s population currently faces.  For example, according to the UN Food and Agriculture Organization every year consumers in the richest countries waste nearly as much food (222 million tonnes) as the entire net food production of sub-Saharan Africa (230 million tonnes).  Nevertheless, the global population numbers given in this review are certainly of concern regarding the sustainability of the planet for future generations:

Human population growth and per-capita consumption rate underlie all of the other present drivers of global change. The growth in the human population now (77,000,000 people per year) is three orders of magnitude higher than the average yearly growth from 10,000–400 yr ago (67,000 people per year), and the human population has nearly quadrupled just in the past century31–33. The most conservative estimates suggest that the population will grow from its present value, 7,000,000,000, to 9,000,000,000 by 204531 and to 9,500,000,000 by 2050.  ( ‘Approaching a state shift in Earth’s biosphere’ 486, 7401. Nature)

Here are a few other stats from the review to think about:

  • 43% of Earth’s land has been converted to agricultural or urban landscapes, with much of the remaining natural landscapes networked with roads.
  • Humans commandeer 20–40% of global net primary productivity (NPP) and decrease overall NPP through habitat degradation.
  • Through the release of energy formerly stored in fossil fuels, humans have substantially increased the energy ultimately available to power the global ecosystem.
  • Burning fossil fuels has increased atmospheric CO2 concentrations by more than a third (35%) with respect to pre-industrial levels.
  • Higher CO2 concentrations have caused the ocean rapidly to become more acidic, evident as a decrease in pH by 0.05 in the past two decades (see Tipping point for coral reefs?).
  • The speed at which plant species will have to migrate to keep pace with projected climate change is greater than their dispersal rate when Earth last shifted from a glacial to an interglacial climate.
  • 43% of Earth’s terrestrial ecosystems have undergone wholesale transformation.
  • 50% of Earth’s land will have undergone state shifts when the global population reaches 8,200,000,000, which is estimated to occur by the year 2025.
  • 70% of Earth’s land could be shifted to human use (if the population reaches 11,500,000,000) by 2060.

All of these facts bring into question how much the human and other species are capable of adapting to rates of change that in some cases it has never experienced before.  I think what many researchers have shown is that the human species in particular has taken for granted its dominance of the Earth’s environment(s) in a way that does not allow for adequate foresight into global-scale problems that threatens its very existence.  The signals that scientists receive by monitoring the Earth’s natural systems are indeed warning signals and how we interpret the ones we’ve seen recent and in the past are of extreme importance to the survival of not merely ourselves, but the entire planet.  The ethical imperative is clear and straightforward, but the actions needed are of another matter.  These are some of the recommendations given:

  • Reducing world population growth and per-capita resource use.
  • Rapidly increasing the world’s energy budget that is supplied by sources other than fossil fuels.
  • Increasing the efficiency of existing means of food production and distribution instead of converting new areas.
  • Enhancing efforts to manage reservoirs of biodiversity and ecosystem services, both in the terrestrial and marine realms.

There is a deep question here of connecting our actions to their consequences as can be understood from the science of today and in the past.  Through remote sensing (see Satellite view of climate change impacts in the arctic) for example nearly anyone with access to the internet can view the levels of ecological devastation at a global scale if they don’t already witness it locally.  But connecting your life with the global environmental systems in place that in turn govern the future of life on Earth is still a difficult pill for many people to swallow, yet immediate gratification received from living in a technological society is also under threat if it cannot be addressed not merely on an international, national, state or community level, but at an individual one.

References and Further Reading

Approaching a state shift in Earth’s biosphere. Nature

Tipping point for coral reefs? IHRR Blog


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