1. Primary Producer (Plant) 2. Primary Consumer (Rabbit) 3. Secondary Consumer (Fox)
When a predatory species becomes threatened or extinct, this removes a check and balance in the food chain on the population of prey previously consumed by that predator. Consequentially, the prey population can explode.
If you remove the Primary Consumer.
A 2002 study identified over 100 species of alien plants known to occur within desert tortoise habitat in the Mojave and Colorado deserts. Many of these species occur in abundance with harmful effects to the ecosystem. The California deserts are high impacted by invasive grasses, such as red brome, cheat grass, and Arab grasses. Native annual grasses are rare, so these invaders have few competitors. Other aggressive invaders include Sahara mustard and Mediterranean mustard as well as salt cedar, which has become established along washes and streams.