Why do food chains become less distinct when specialist species disappear?

Food chains become less distinct when specialist species disappear because of a process known as ecosystem homogenization.1

Specialist species are uniquely adapted to specific environmental conditions, narrow habitats, or limited food resources. When these species go extinct or suffer dramatic population declines, they are often replaced by generalist species—those capable of thriving across a wide variety of habitats and food sources—or by species favored by human activity, such as crops and livestock.1

As these generalists become the dominant players in vacated ecosystems, the unique interactions and specific roles that previously defined the structure of local food chains are lost. Consequently, ecosystems across broad areas begin to lose their complexity and distinctiveness, as their food chains and nutrient-cycling processes become increasingly similar to one another.1