My projections of world consumption of ecological resources suggest that in 1961 the amount of economic activity per unit of consumption was at its historical minimum, translating into $1,425 per hectare in 2009 dollars. In 1980, when humanity was consuming all of the ecological resources produced by Nature (instead of that and the producers themselves, as we are now), a hectare was worth $2,288 and increasing. That number is now $4,123, and is expected to reach a maximum of $4,890 in 2029 when consumption, economic activity, and population also peak.
If it takes a minimum ecological footprint of 1.5 hectares per person to maintain a functioning society, then we could theoretically reduce average consumption to 56% of its current value. We would then be collectively consuming only 88% of what Nature can produce, with the extra as a reasonable amount for the producers to consume (as well as a margin for error). Economic activity, measured as Gross World Product (GWP), would be 26% of its present value if the historical relationship between consumption and GWP held, which would be 48% of current per-capita GWP.
Based on national ecological footprint data from the Global Footprint Network, an estimated 41% of the world's population consumed less than 1.5 hectares in 2007 (the world average was 2.7). In a fair world, their consumption would need to be increased at the expense of those of us with a surplus. Also in a fair world, population would stay constant along with consumption; the cost of increasing per-capita consumption for a few would unfortunately be taken in lives from others.
Of course, the real world is much more complex than this discussion assumes. For example, ecological resources are not evenly distributed around the world; it will take resources to either move resources where they're needed, or move people where the resources are. Pollution already in the atmosphere and water threaten to reduce the total amount of resources available, which would force part of the world's population below the minimum consumption threshold even in the best case. Obviously, I've ignored the huge political, social, and economic barriers to such a monumental redistribution of wealth, which will likely make the other complications moot.
As individuals, we can at least try to improve the situation. We can work on cutting our consumption as much as possible (starting with half), using the rest to pay off debt and then finding ways to get it to the people consuming less than the minimum. Our sources of income will need to migrate from resource-intensive (and especially extractive) activities to those that increase Nature's production. This will have an added benefit of reducing additional pollution and giving other species a chance to process the waste we've already dumped. For those of us who loathe the greedy actions of enthusiastic planet-killing sociopaths such as Wall Street bankers and leaders of the fossil fuel industry, our elimination of debt and unwillingness to purchase their products -- now and in the future -- will reduce the capital they have to do more damage. With any luck, what we do will have a cumulative effect large enough to make a significant difference, but at least we'll be able to sleep better at night with somewhat clearer consciences.