The world overshoot day – are we consuming 1,5 planets a year?

I suppose it is common knowledge these days to remind ourselves that today is the day when “humanity has exhausted nature’s budget for the year.” In other words humanity spends earth’s annual biocapacity’s worth of resources in only a bit over eight months. Moreover, the time required to reach this point takes less and less time each year.


I think it is hugely important to care for the environment and I can certainly understand the need for campaigns that are aimed at raising awareness over the fact that human well being can have a detrimental impact on the environment.

Very few people who know about the world overshoot day seem to be aware of the metrics how the overshooting day is calculated.

I mean, what does it really mean that humanity requires resources worth 1,5 earths?

The most widely used Ecological Footprint (EF) methodology has been developed by the Global Footprint Network. It includes six metrics that include carbon emissions, built-up land, cropland, grazing land, forest land and fishing ground. The bottom line is that each of these metrics are looked at in the context of whether humanity uses more of “it” than the globe annually produces/absorbs and the sum of all these factors formulate the net impact.

Do the numbers add up?

Interestingly, out of the six metrics humanity is not really doing any overshooting at all and it is only in one metric – carbon emissions – that we tilt the balance deep on the red side.


I am not arguing that we should ignore carbon emissions – it is an important indicator of humanity’s impact on the environment but it is the way the earth’s ability to absorb carbon emissions has been calculated that can be considered problematic. A fairly recent paper that was published in the journal, Plos Biology, was highly critical of the EF methodology in few regards.

Firstly, the paper argues that a lot of environmental problems can be easily overlooked as a result (e.g. water scarcity, extinctions). Secondly, if humanity’s ecological impact is determined virtually by the carbon footprint alone it is hugely important that it is determined as accurately as possible. The EF has done this by calculating how big of an area of forest the earth would need in order to “sequester all net anthropogenic emissions of carbon dioxide”. The rate at which forests absorb CO2 is based on the assumed global average (CO2) absorption rate of forests.

There are some problems in using such fairly arbitrary method. Different assumptions in earth’s forests’ ability to sequester carbon dioxide could either lead to a result that we are not overshooting earth’s carrying capacity at all (young forests) or that we would need almost an infinite number of planets (if forests become net carbon emitters at some point).

Instead of accurately describing global environmental well-being, the method merely limits humanity’s impact on one susceptible metric alone. A similar global tool could be useful but this sort of simplification that is dressed up as valid and sound scientific methodology for assessing state of the global environment and then popularized as the true indicator of how we are doing is simply not good enough.

A prescription for disaster?

On the world overshoot day I hear a lot of calls for more sustainable living (another popular but vague term that’s significance I will someday look at). On a day that is supposedly calling for limiting humanity’s impact on the environment and especially its carrying capacity, some of the calls seem to be truly counter-intuitive. For example, organic farming requires more land area for the same yield as traditional intensive farming and renewable energy sources require vast areas of land (esp. biomass) and other resources compared to more concentrated forms of energy production. While I do not want to condemn either, it is fairly problematic to call for a more limited impact on the planet with measures that would in fact increase the burden of the earth’s biocapacity.

As I have argued, humanity has in fact been fairly successful in limiting its relative impact on the environment over the history. The ratchet-like development of technology will be essential that our impact will be further reduced still, especially at the onset of the birth of the global middle-classes.

It is important to raise people’s awareness over environmental and other problems but sometimes these methods are in danger of overshooting themselves.

One comment

Convince me I am wrong and I will promise to change my mind!

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s