Top 10 Worst Invasive Species

Originally from Southeast Asia, this aggressive daytime biter now spans every continent except Antarctica, transmitting dengue, Zika, and chikungunya to millions of people annually.

Released pet pythons have established a breeding population of tens of thousands in Florida's Everglades, devastating native mammal populations including marsh rabbits, raccoons, and opossums by over 90 percent.

These fingernail-sized molluscs from the Caspian Sea clog water intake pipes, smother native mussels, and reshape entire Great Lakes food webs, costing North America over $1 billion annually.

This fast-growing plant can crack through concrete and tarmac, costing the UK alone an estimated £166 million annually in property damage and reducing affected house values by up to 15 percent.

After arriving on Guam as a stowaway after World War II, this nocturnal predator wiped out 10 of the island's 12 native forest bird species and causes frequent power outages by climbing electrical lines.

Indo-Pacific lionfish have invaded the Caribbean and western Atlantic, consuming over 30 species of native fish and crustaceans with no natural predators to control their explosive population growth.

Introduced to Australia in 1859, rabbits spread across the continent within decades, causing catastrophic soil erosion and driving native plant species to extinction through relentless overgrazing.

This South American aquatic plant forms dense mats that choke waterways across Africa and Asia, blocking sunlight, depleting oxygen, and devastating fisheries that millions of people depend on.

Feral cats kill an estimated 1.3 to 4 billion birds annually in the United States alone and have contributed to at least 63 species extinctions worldwide, yet cat culling programmes face fierce public opposition.

Originally from Southeast Asia, this aggressive daytime biter now spans every continent except Antarctica, transmitting dengue, Zika, and chikungunya to millions of people annually.

Released pet pythons have established a breeding population of tens of thousands in Florida's Everglades, devastating native mammal populations including marsh rabbits, raccoons, and opossums by over 90 percent.

These fingernail-sized molluscs from the Caspian Sea clog water intake pipes, smother native mussels, and reshape entire Great Lakes food webs, costing North America over $1 billion annually.

This fast-growing plant can crack through concrete and tarmac, costing the UK alone an estimated £166 million annually in property damage and reducing affected house values by up to 15 percent.

After arriving on Guam as a stowaway after World War II, this nocturnal predator wiped out 10 of the island's 12 native forest bird species and causes frequent power outages by climbing electrical lines.

Indo-Pacific lionfish have invaded the Caribbean and western Atlantic, consuming over 30 species of native fish and crustaceans with no natural predators to control their explosive population growth.

Introduced to Australia in 1859, rabbits spread across the continent within decades, causing catastrophic soil erosion and driving native plant species to extinction through relentless overgrazing.

This South American aquatic plant forms dense mats that choke waterways across Africa and Asia, blocking sunlight, depleting oxygen, and devastating fisheries that millions of people depend on.

Feral cats kill an estimated 1.3 to 4 billion birds annually in the United States alone and have contributed to at least 63 species extinctions worldwide, yet cat culling programmes face fierce public opposition.