Humans have already used up 2015's supply of Earth's resources – analysis | Environment | The Guardian
http://www.theguardian.com/environment/ ... s-analysis

We're a profligate bunch, but I'm extremely dubious about the notion that the earth somehow has a 'quota' of resources each year. It's something I can't imagine any respectable scientist doing.

Surely it just depends on the bounds of whatever metrics you're measuring?
As in: "The date is based on a comparison of humanity’s demands – in terms of carbon emissions, cropland, fish stocks, and the use of forests for timber – with the planet’s ability to regenerate such resources and naturally absorb the carbon emitted. That implies the excess demands being placed on natural systems are doing more permanent harm that cannot be easily undone."

Indeed. It also assumes you actually know at what rate the planet's resources are being regenerated - how many trees are growing, how many fish are being born, how many acres of crops will be sewn for next year etc. I suspect very many of the those calculations are 'finger in the air' at best.

You can get pretty accurate figures on crops these days and with forestry a major business, deforestration and replanting are fairly well planned these days - yes, it won't cater for the odd trees that propagate themselves, but that is a relatively small number, compared to managed forests and the amount of wood that we chop down each year. We run one of the biggesst agricultural certification platforms in the world, there are hundreds of thousands of farms registered and they register their crops and get them certified, so that they can sell them on the open market. Again, it might not cover 100% of farming, but it probably cover over 90% of commercial farming worldwide, so you have a good basis for calculating.

Then you have to take into account forests that are dying out. We were in Harz a couple of years ago and vast swathes of the forests there were dying off.

Fish will probably be based on trends, again we fish so heavily these days and it is commercial, so we have trends for several years to predict birth and death / capture rates.