How much of the Solar System should we leave as wilderness?
Martin Elvis a , Tony Milligan b 2019

Highlights
• Solar System resources are vast, but finite.
• Normal exponential growth suggests 400 years before exhaustion is approached.
• Prudent to adopt a “1/8 Principle” as a tripwire: “Do not exploit >1/8 of Solar System”.
• Rest should be left as Wilderness.
• Many ethical and practical questions must then be dealt with.


“How much of the Solar System should we reserve as wilderness, off-limits to human development?” We make a general argument that, as a matter of fixed policy, development should be limited to one eighth, with the remainder set aside. We argue that adopting a “one-eighth principle” is far less restrictive, overall, than it might seem. One eighth of the iron in the asteroid belt is more than a million times greater than all of the Earth's currently estimated iron ore reserves, and it may well suffice for centuries. A limit of some sort is necessary because of the problems associated with exponential growth. We note that humans are poor at estimating the pace of such growth and, as a result, the limitations of a resource are hard to recognize before the final three doubling times. These three doublings take utilization successively from an eighth to a quarter, then to a half, and then to the point of exhaustion. Population growth and climate change are instances of unchecked exponential growth. Each places strains upon our available resources, each is a recognized problem that we would like to control, but attempts to do so at this comparatively late stage in their development have not been encouraging.
Our limited ability to see ahead until such processes are far advanced, suggests that we should set ourselves a “tripwire” that gives us at least 3 doubling times as leeway. This tripwire would be triggered when one eighth of the Solar System's resources are close to being exploited. The timescale on which we might hit this tripwire, for several assumed growth rates, is long. At a 3.5% growth rate for the space economy, comparable to that of the use of iron from the beginning of the Industrial Revolution until now, the 1/8th point would be reached after 400 years. At that point, the 20-year doubling time associated with a 3.5% growth rate would mean that only 60 years would remain in which to transition the economic system to new “steady state” conditions. The rationale for adopting the one- eighth principle so far in advance is that it may be far easier to implement in-principle restrictions at an early stage, rather than later, when vested and competing interests have come into existence under conditions of diminishing opportunity.