It is the mission of nearly every mainstream economist to overcome the pessimism of those who study the natural world and who don't see how the human endeavor can continue on its current course of endless exponential economic growth. "Now, now," these economists will say to the natural scientists, "you are being alarmist just like many before you. Let the marketplace work its wonders and let economic prosperity come to all parts of the world and this will enable us with our newfound wealth to address the many environmental problems we need to face."
Such arguments seem like mere nonsense to any scientist who believes that endless economic growth is the cause of those problems. But the difference between these two camps may be less than it appears. Enlightened economists do acknowledge the need to treat the environment which sustains us with more care. The main issue appears to be timetables.
Most economists believe that we are not in any imminent danger of societal collapse. We have plenty of resources and the big problem of global warming can be solved by taxing or otherwise restricting the use of carbon-based fuels. New technologies will give us what we need, in time and affordably. It has always been thus. (Except when it hasn't. But one would have to know the history of civilizations that did succumb to resource degradation and scarcity, and most economists are very much concerned with the utterly now.)
To the scientist who worries about sustainability and perhaps more urgently about the availability of enough energy, particularly oil, to run our society, this leisurely attitude seems quite dangerous. Partly, this is because the cheap fossil fuel energy we now enjoy will be needed to build the next energy economy. If we as a global society wait until the last minute to begin building that new energy economy, we may not have enough fossil fuels to do it. Those fuels may decline faster than we can replace the energy we currently get from them. This is often referred to as the rate-of-conversion problem.
Let us see how these different timetables might effect world society.
For the economist failure to grow would condemn billions to poverty, disease and ignorance. (Never mind that billions are condemned to that under the current system; but this is only because, as the economist will tell us, we haven't gone far enough with the spread of global capitalism.) If enough of the poor become middle class, their societies will undergo what is called the demographic transition. Birth rates will fall and so will death rates, and the population will level out or at least grow much more slowly. (Never mind that the true impact on the biosphere comes from per capita consumption and pollution times population, not population alone. Greatly increasing per capita consumption while slowing or ending population growth will not necessarily solve any environmental problems.)
But the path offered by my hypothetical economist is one without recourse. Once we commit to it, there is no going back. If the economist turns out to be wrong about the availability of resources or about the severity and pace of climate change, then global society could very likely face a fatal blow from which it cannot recover. There may be no second chance.
Let's look at an alternate path. If instead global society works very hard in the short term to curtail resource use and economize on energy use in an effort to reduce the throughput of physical resources radically, we may be able to build a highly efficient global economy that gives us many of the same services we have now. (Remember, it is not goods per se that we want, but the services they provide. We may want a car, but we want it because it is a convenient form of transportation. We seek the service of transportation.)
If we as a global society choose this path, and then it turns out that the pessimists in the scientific community are wrong about the severity of climate change and the availability of resources--that is, climate change turns out to be a minor problem and resource availability is much greater than anticipated by the pessimists--if this is the case, then we could choose to resume economic growth and use more resources to support it. In short, we would have a second chance to achieve the growth which the enlightened economist deems as necessary for the salvation of the poor. But we would do it within the context of a highly efficient, low-polluting system that tries to achieve all desired goals with minimal resource usage.
It is the asymmetry of risk in these trajectories that ought to give growth-oriented economists pause. Perhaps the economists will say that the risks simply aren't there. But then the record of most economists in predicting anything, even the direction of markets and market economies about which they presume to have specialist knowledge, has been nothing sort of dismal. Furthermore, the economists can give us no warranty for our society if it collapses under the weight of resource depletion and climate change. Wouldn't the more prudent path be to ensure that we don't have to face that possibility? Is the imperative for growth so great that we should risk the annihilation of our society in order to achieve it?