Because of the open-access nature of the environment we consider an ad hoc adjustment of people's environmentalfootprint to the quality of the environment. The adjustment is motivated by environmental concern,but hindered by skepticism about announced changes in the state of the environment. Changes in the qualityof the environment affect Earth's carrying capacity. By expanding the Lotka–Volterra predator–prey model toinclude these features we show that, despite skepticism, the environment does not deteriorate to a state inwhich humans cannot exist. We also show that in the ideal case of no skepticism, the interplay betweenthe non-optimally changing environmental concerns and carrying capacity leads the world's environmentand human population to a unique interior steady state along an oscillating course. These results requireno further technological, social or international progress.