We consider a stock pollution problem where the biosphere can transform from a sink to a source of pollution in the presence of self-regenerating environmental absorption efficiency. We examine the problem of controlling pollution and the capacity of the biosphere to absorb pollution: the regulator can mitigate emissions and can invest to build up the absorption capacity of pollution sinks. We examine conditions under which both measures, mitigation and absorption capacity investments, are substitute (complement) to each other, and the relative extent to which environmental self-regenerating capabilities affect these conditions. We also exhibit the possibility of an oscillatory approach to the steady state. Particular attention is paid to the situation where the social planner is impatient.