In ecosystems with more biodiversity the food webs and ecological interactions among living beings are more complex and diverse. In these ecosystems environmental changes can be more easily compensated by the multiplicity of available resources, foods and survival options.
In ecosystems with less biodiversity the individuals are more dependent on some beings that serve them as food and they interact with a small number of different species. In these ecosystems generally abiotic factors are restrictive and the species are more specialized to such conditions and more sensitive to environmental changes. So even small environmental harm can cause big disturbances in the equilibrium of the ecosystem.