Conceptual Issues Framing an Assessment of Human Impacts of Earth Systems

Preamble: An existential crisis occurs when an impact is so great that it is transgenerational in scope and terminal in intensity.
Qs Are human impacts on Earth systems existential risks, or are they globally endurable? What other disciplines assess global risk?

A. In conformity with the “uniformitarian” guiding principle (Lyell et al), we should regard ourselves as products of the same ecological and evolutionary forces that produced all other species.
Qs If nature produced us, are we natural? Is “catastrophism” compatible with uniformitarian principles?

B. Just as amoebae acquired pseudopodia and the aardvarks their long protruding tongues as a way in which it survives, we humans benefit from certain evolutionary legacies: for example bipedalism, cognitive complex, technical know-how and a capacity for culture. These sufficed to keep humans in the evolutionary game during the tough times, but appear to have “overproduced in times of plenty.”
Qs Is cultural change part of our evolutionary toolkit, or is it distinct from all other evolutionary products? What is it to be human from an environmental perspective?

C. One of our evolutionary peculiarities, humans relative flexibility in life history strategies, which flexibility allows for cultural influences on our birth and death rate regimes, facilitated our transition from a rare tropical species to one that is now ubiquitous and with a population size of almost 7.2 billion.
Qs Are there other species that once were rare and now very common?  Why was the transition to agriculture so consequential from a human life history perspective?

D. By many metrics including carrying capacity, ecological footprint, and the human appropriation of net primary productivity (HANPP) — each with some inherent limitations and uncertainties — we are imposing unsustainable impacts upon the natural world and its ability to furnish us with the goods and services we need.
Qs Is there a limit to human numbers, or are humans their own limitless “ultimate resource?” 

E. Fortunately, not all aspects of nature are inherently fragile: many systems have incorporated a degree of “resilience” in the response to impacts (either from human or non-human sources). Admittedly, we have not been historically adept at distinguishing resilient from friable ones.
Qs Distinguish engineering from ecological resilience? If disturbance is incorporated as an inevitable component of “adaptive cycles” is it possible to categorically distinguish human-inflicted disturbance from disturbance emanating from the rest of nature? [Ecology's "God is Dead" moment!]

F. Recent conceptual advances in our ecological understanding invite us to jettison notions of balance, climax community, steady-state systems, and linear change. Replacing the “old ecology” are notions that multi-state systems, integral disturbance, critical transitions, ecological resilience.
Qs Does resilience thinking not merely smuggle the language of balance back into ecology? [Extra points: use your understanding of panarchy to foment world revolution.]

G Tasks for the future include being able to assess impact with reference to the resilience of systems, and, for those with an engineering or management orientation, and building resilience into systems that are likely to catastrophically flip to less desirable states.
Qs What are the essential features of a resilience complex adaptive system such as a human-dominate landscape? Is there a role for ethics - also, presumably, and evolved human characteristics - in determining our relationship with the rest of nature?