Modern humans have been on earth for 200 centuries. True sustainability means providing every person now alive, as well as generations yet to come, with a reasonable standard of living which can be maintained into the foreseeable future.
Today humanity uses the equivalent of 1.5 planets to provide the resources we use and absorb our waste. This means it now takes the Earth one year and five months to regenerate what we use in a year.
Present lifestyles in the richer countries have a disproportionate impact, for example the ecological footprint per capita of the USA is more than ten times that of Malawi or Mozambique.
Some expenditure, such as that on arms spending or promotional activity, could be arguably reduced if society’s focus was more on human happiness and less on GDP growth and state and commercial competition.
As individuals, there are several things that you can do to help ensure that the world is worth living in for future generations.
As prospective parents, you can decide to have only one or two children. This will probably be the most environmentally important decision you ever make.
As individuals, you can support Population Matters and help raise awareness of the issue. The more widely it is discussed, the more widely population will be recognised as one of the key drivers of the looming environmental crisis, and the sooner any remaining notion that it is a 'taboo' subject will disappear.
As media customers, you can complain about articles and programmes which discuss sustainability or the environment yet ignore population even though it is relevant.
As voters, you can ask your local and national political leaders to recognise national and global population growth as a serious environmental problem.
Finally, as citizens, you can contribute by consciously living more sustainably in other ways; this depends both on big decisions such as whether to go on a long-haul flight and also on the large number of choices we all make on a day-to-day basis: waste less, re-use and recycle more, resist the blandishments of our consumer culture and decide which 'benefits' of modern society really matter to you.
The most important personal decision we can make about our long-term impact on sustainability is almost certainly the number of children we have.
Read more about things individuals can do to reduce their consumption of resources.