  In the light of current scientific assessments of human-induced climate
change, we investigate an experimental model to inform how resource-use
strategies may influence interplanetary and interstellar colonisation by
intelligent civilisations. In doing so, we seek to provide an additional aspect
for refining the famed Fermi Paradox. The model described is necessarily
simplistic, and the intent is to simply obtain some general insights to inform
and inspire additional models. We model the relationship between an intelligent
civilisation and its host planet as symbiotic, where the the relationship
between the symbiont and the host species (the civilisation and the planets
ecology, respectively) determines the fitness and ultimate survival of both
organisms.
  We perform a series of Monte Carlo Realisation simulations, where
civilisations pursue a variety of different relationships/strategies with their
host planet, from mutualism to parasitism, and can consequently 'infect' other
planets/hosts. We find that parasitic civilisations are generally less
effective at survival than mutualist civilisations, provided that interstellar
colonisation is inefficient (the maximum velocity of colonisation/infection is
low). However, as the colonisation velocity is increased, the strategy of
parasitism becomes more successful, until they dominate the 'population'. This
is in accordance with predictions based on island biogeography and r/K
selection theory. While heavily assumption dependent, we contend that this
provides a fertile approach for further application of insights from
theoretical ecology for extraterrestrial colonisation - while also potentially
offering insights for understanding the human-Earth relationship and the
potential for extraterrestrial human colonisation.
