Anytime you wish to trouble us with some science please do so, your ad homs are less than enlightening.
Malthusian catastrophes are not 'faith' but regularly documented population crashes in ecological science. They have also affected humans throughout their history. 3 examples that spring to mind rather immediately are the Polynesian populations of Pitcairn and Henderson islands, Kangaroo Island in South Australia and the Norse Greenland colonies. All three are isolated human populations that, like the reindeer died out due to over consumption of resources or ecological changes. The latter had metal working tool, literacy and advanced tool kits, but they died out when far more ‘primitive’ Neolithic tooled peoples survived in the same environment.
Other good examples of population crashes are the Easter Islands where the over consumption of a vital renewable resource (wood and birds) left the islands with a huge problem of overshoot. The population is thought to have crashed from c.15 000 to c.2000 in around 100 years (the numbers and timelines are not firm).
The period in European history following the Great Famine (1315-1317).
http://en.wikipedia.org/wiki/Great_Famine_of_1315-1317
The population of Europe had been sustain at very high levels by the gentle climate of the Medieval warm period but the population had reached its maximum. All it took was two bad harvests and it set of a chain of events that seen Europe’s population plummet to dramatically lower levels.
The collapse of the Mayan civilisation in Southern Central America is often strongly linked to drought and water mismanagement leading to a collapse of the complex society and a subsequent population collapse.
The list of population crashes from changes in climate or environmental degradation is long and well documented.
Understanding that it is possible is the first necessary to opening a dialogue on mitigation against these potential threats.