All of the consumers would be affected, and be forced to adapt. Since the amount of grass has decreased, the primary consumer would struggle to survive, and most likely, die out. Since the primary consumer has probably died out, the secondary would either die, or be forced to adapt to the situation, or change habitats ( applies to the rest in the food chain / web).
Introducing exotic species into new environments is not recommended for biodiversity conservation because it can cause proliferation of invasive species. This can cause ecological problems, a threat to native organisms and it can affect the economy and human health.
