The idea that reserves and national parks formed islands inside human-altered landscapes (habitat fragmentation), and that these reserves could lose species as they 'relaxed towards equilibrium' (that is they would lose species as they achieved their new equilibrium number, known as ecosystem decay) caused a great deal of concern.
A idea de que as reservas e os parques naturais forman illas dentro do espazo alterado polos humanos (véxase, fragmentación do hábitat), e que esas reservas poderían perder especies por actuar «relaxándose cara ao equilibrio» (isto é, que perderían especies xa que conseguen o seu novo equilibrio ca perda de especies, o que se coñece tamén como decaemento do ecosistema), causou un amplo debate de preocupación.