Answer to Question 1
For all of human history this has been true, but only if we neglect the input of
energy from the Sun That is not really self-sufficiency. In the future, off-Earth resources
will become more important.
Answer to Question 2
There are several problems with exploitation of oil shale (as with oil sands), as
was discovered during the 1970s push to develop this as an energy resource. A lot of water
must be used to extract the oil from the rock, and the region containing the oil shale is the
mountain west, which is generally poorly watered. Further, the shale expands as it loses the
oil, causing a tailing problem from mining and a possible leaching problem later on. Unless
the cost of oil is far greater than that of water in situ, and the local people are ready to accept
the environmental disruption, it is not likely that large scale exploitation will occur.
