This year, renewable resources have been exhausted and the planet has been overloaded

Earth Overload Day was celebrated on August 1 last year, three days later than this year.

Monday, July 29, the 209th day of 2019. On this day mankind has used up all the resources that the Earth can regenerate in 365 days.

The special day is the result of calculations by the Global Footprint Network, which uses United Nations data to calculate Earth Overload Day: It's a day when humans are consuming resources faster than the planet can reproduce them -- the trees we cut down, the carbon dioxide we emit, the fish we catch, to name a few. At current rates of resource consumption, the Global Footprint Network estimates that at least 1.75 Earths are needed to sustainably meet human demand.

Earth Overload Day provides us with an extremely important "visual sense" of the finite nature of our planet's resources. But what is even more shocking is that the Earth Overload Day calculations may have vastly underestimated the destructive power of unsustainable development, and that the scientists responsible for the calculations are the first to admit it.

David Lin, chief scientist at the Global Footprint Network, likes to use the analogy of a bank account: "If you only have $100 in your bank account and you spend $200, you're going to be in the red; If you continue to live in this way, consuming things you don't have, then eventually you're stuck -- it's an unsustainable lifestyle."

Every year, the Earth's population grows. We consume more natural resources than the Earth can produce in a year, and emit far more carbon dioxide than our forests and oceans can absorb. As a result, our resource liabilities have grown and our resource deficits have grown. Earth Overload Day fell on August 1 last year, three days later than this year. In the past 20 years, the date has been advanced by two full months.

This year's Earth Overload Day is the earliest ever.

Earth Overload Day calculations rely heavily on a range of country-level data and global figures from the United Nations, which include the amount of food produced and consumed in each country, the amount of waste produced, the amount of wood cut and the amount of fossil fuels burned. Calculations for Earth Overload Day are limited by the quality of global data, which may be underestimates at their root. Research shows that the UN Food and Agriculture Organization's estimate of global seafood catch may be 30% lower, but given the current conditions, the UN's data are the best and most accurate, so Earth Overload Day is calculated using the UN's data.

David Lin is one of four researchers who spend six months a year crunching the numbers. "What we're doing is so important that all of the resources that humans consume, and all of the waste that humans produce, can be reflected by our calculations in the area of biological production that they need."

They also calculated Earth Overload Day separately for each country: the United States on March 15, Australia on March 31, and Qatar on February 11.

If the world's population consumed natural resources and produced waste at U.S. levels, we would need five Earths to keep up with these demands.

Each country has its own Earth Overload Day, which is calculated based on the amount of resources it consumes, the amount of waste it produces, and the space available for biological production.

Earth Overload Day is an eye-catching number, but in fact it hardly gets to the bottom of the problem. For example, Earth Overload Day is calculated without taking into account soil degradation, water pollution or large-scale species loss -- because it's not an indicator designed for that. Earth Overload Day is a simple calculation of current levels of resource consumption and production. It does not take into account how many resources will be used up by human activities in the future, and it does not reflect some ecological damage that has no impact on humans.

"Earth Overload Day is often misunderstood as an indicator of the sustainability of everything, but it's not. In fact, there is no such thing as a 'universality indicator', which is theoretically impossible. "

The global data that underpins such global indicators do not exist. At the very least, even if the data did exist, scientists would have to choose a time parameter for what they call "sustainability." Five years? Or ten years? No one has an answer.

Earth Overload Day does not consider whether our current levels of agricultural production will destroy soil resources on which future generations of humans depend, or whether current groundwater pumping will lead to desperate water shortages in a few years. David Lin said, "Earth Overload Day reflects the current sustainability of the planet, not the future. Earth Overload Day is a snapshot of the current level of resource deficit on the planet, but the future viability of the planet depends on far more resources and conditions than this number can capture. You may be able to sell your kidney for money, and your bank account may look good that year, but you should know it's not sustainable.

To be sure, the situation we face is far worse than Earth Overload Day reflects. But Earth Overload Day can serve as a minimal indicator of the problems we face. David Lin said, "Even if we only use this minimum measure, our planet is still overloaded. But in the current conditions, we don't have a better global measure, and no one has come up with a better method."