En 10 mois, l'humanité a épuisé le budget de la nature pour l'année/In 10 months, humanity has exhausted nature’s budget for the year

Publié le par revivall

Aujourd'hui 27 septembre, nous avons déjà dépensé plus de ressources naturelles que ce dont nous disposions pour l'année. C'est ce qu'affirme l'ONG Global Footprint Network, qui calcule chaque année notre «budget» de ressources naturelles, et le jour où nous le dépassons. Au-delà de ce jour, nous utilisons des ressources que la planète ne peut pas regénérer.

Cette année, nous aurons donc mis neuf mois à consommer les ressources prévues pour douze, puisant dans nos stocks en diminution d'arbres et de poissons, accumulant le CO2 dans l'atmosphère et les océans.

Pendant une grande partie de notre histoire, nous avons utilisé les ressources naturelles à un rythme que la planète pouvait «suivre». Mais depuis les années 1970, nous sommes chaque année en «dépassement écologique».

Le président de l'ONG explique dans un communiqué:

«C'est comme si vous dépensiez votre salaire annuel trois mois avant la fin de l'année, et que vous puisiez dans votre épargne année après année. Assez rapidement, vous n'avez plus d'épargne.»

Le dépassement écologique est déterminé par trois facteurs, résume l'AFP: la quantité de ressources que nous consommons, la population globale, et la quantité de ressources que la nature peut produire.

D'après l'ONG, en 2011 nous aurions au total eu besoin d'entre 1,3 et 1,5 planète pour que les ressources naturelles que nous utilisons se régénèrent.

Et ce n'est pas près de s'arranger si nous ne modifions rien à notre comportement: l'an dernier, le World Wildlife Fund affirmait que nous aurions besoin d'une deuxième planète pour subvenir à nos besoin d'ici à 2030, et de l'équivalent de 2,8 planètes d'ici à 2050.

Les océans s'acidifient, incapables d'absorber les taux de dioxyde rejetés par la planète. WWF, qui a étudié différentes espèces animales, a montré une baisse de 30% de la population entre 1970 et 2007. Les pays riches ont «seulement» connu une perte de biodiversité de 5% entre 1970 et 2007, contre 25% pour les pays moyennement riches, et 58% pour les pays pauvres. Les personnes les plus affectées par la dégradation de leurs ressources naturelles sont donc les populations qui se reposent le plus sur celles-ci, notait alors le Time.


Similarly to the way a bank statement tracks income against expenditures, Global Footprint Network’s methodology tracks human demand on nature – from filtering CO2 to producing the raw materials for food – against nature’s capacity to regenerate those resources and absorb the waste. Our research shows that in approximately nine months,  we have demanded a level of services from nature equivalent to what the planet can provide for all of 2012. We maintain this deficit by depleting stocks of things like fish and trees, and by accumulating waste such as carbon dioxide in the atmosphere and the ocean.


Earth Overshoot Day (based on a concept devised by UK-based new economics foundation), helps conceptualize the degree to which we are over-budget in our use of nature. While meant as an estimate more than an exact date,  Earth Overshoot Day helps conceptualize the size of the gap between a sustainable level of ecological demand and how much is currently required to support human activities globally.



The Cost of Ecological Overspending

Click here to watch a video on overshoot

For a vast majority of human history, humanity has used natures’ services – to build cities and roads, to provide food and create products; and to absorb the CO₂ generated by human activities - at a rate that was well within the means of what nature could regenerate. But, sometime in the mid 1970’s, we crossed the critical threshold. Human demand on nature began outstripping what it could renewably produce, a condition known as ecological overshoot.


Global Footprint Network’s preliminary 2011 calculations show we are now using resources at a rate that would take between 1.3 and 1.5 planets to sustainably support. Our research shows us on track to require the resources of two planets well before mid-century.

Of course, we only have one Earth. The fact that we are using (or “spending” natural capital) faster than it can replenish is similar to having expenditures that continually exceed income. In planetary terms, the results of our ecological overspending are becoming more clear by the day. Climate change – a result of carbon being emitted faster than it can be reabsorbed by the forests and seas – is the most obvious and arguably pressing result. But there are others as well: shrinking forests, species loss, fisheries collapse and freshwater stress to name a few. The environmental crises we are experiencing are all symptoms of an overall trend—humanity is simply using more than the planet can provide.

Have We Reduced Global Overshoot?

Earth Overshoot Day (based on a concept devised by UK-based new economics foundation) helps conceptualize the gap between what nature can regenerate,and how much is currently required to support human activities.  But it is not, of course, possible to determine with 100% accuracy the exact moment we bust our budget. We are constantly working toward better data sets and methods that can help us more accurately capture the extent to which human demand exceeds nature’s supply, but it is not possible to count every fish.  Hence, Earth Overshoot Day is meant as an estimate rather than as an exact date.

Ecological Footprint and biocapacity calculations Global Footprint Network made last year placed Earth Overshoot Day a few weeks earlier in the year than this year’s estimates do. This has raised the question as to whether we have reduced global overshoot.  The answer, unfortunately, is no.  Global Footprint Network is constantly improving the calculations and data sets that are the basis for determining Earth Overshoot Day, and as such the date of Earth Overshoot Day varies from year to year.

Currently, we are undertaking some revisions to the way we compare productivity across different geographies and land types – how we incorporate the output of a forest in Russia, for example, and fishing ground in Chile into a single standardized number.  If we look at where Earth Overshoot Day would have fallen over time based on these new assumptions (which we are still testing), we would see overshoot continuing to grow slightly year over year. (See the Media Backgrounder for more information, and to see when Earth Overshoot Day would have fallen over time using our most current assumptions.)

Our methodology does change and may continue to shift, but no matter what scientific approach we have used, and what improvements we have implemented to try to account for both human demand and nature’s supply, the trends remain consistent: we are in significant overshoot, and overshoot is growing.  By any analysis we are well over budget, and that debt is compounding.

The when is less important than the what: a mounting ecological debt, and the interest we are paying on that debt –food shortages, plummeting wildlife populations, disappearing forests,degraded land productivity and the build-up of CO2 in our atmosphere and ocean, with devastating human and monetary costs.


How is Earth Overshoot Day Calculated?

Put simply, Earth Overshoot Day shows the day on which our total Ecological Footprint (measured in global hectares) is equal to the biocapacity (also measured in global hectares) that nature can regenerate in that year. For the rest of the year, we are accumulating debt by depleting our natural capital and letting waste accumulate.

[ world biocapacity / world Ecological Footprint ] x 365 = Earth Overshoot Day

It is not, of course, possible to determine with 100% certainty the exact moment we bust our budget. We are constantly working toward better data sets and methods that can help us more accurately capture the extent to which human demand exceeds nature’s supply, but it is not possible to count every fish.

This year, because we are still in the process of developing the global Ecological Footprint numbers that are the basis of the Earth Overshoot Day calculation, we chose a date representing a day within the lower part of the overshoot range.

Hence, the date is meant as an indication rather than an exact date. But while we cannot pinpoint the exact day we cross the threshold, we know we now are moving into an unsustainable level of resource demand for the year, and well before the year is over.

Click here to learn more about Earth Overshoot Day, and how it has changed over time.


Source: footprintnetwork.org

Publié dans Actualité

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