Even using their own highly questionable numbers, anti-immigrant activists may be barking up the wrong tree. What's the bigger threat: illegal aliens, or invasive species? We report, you decide.

Mode of entry	Porous U.S. borders	Porous U.S. borders
Annual cost to the U.S. taxpayer	Lou Dobbs: $100 billion	$120 billion
Estimated population inside the U.S.	Dobbs: Up to 20 million	At least 50,000 distinct species comprising trillions of individuals. 16 invasive plant species alone cover 126 million acres of U.S. land. 80% of U.S. fish populations have been degraded by invasive species.
Health threats	WorldNetDaily: Drug-resistant Tuberculosis, Chagas disease, Dengue fever, Polio, Hepatitis A, B, and C	AIDS, Malaria, Typhus,  Plague, West Nile virus, Cholera, Mad Cow Disease, Avian Flu
Accused of:	Stealing U.S. jobs, living off of the welfare system, and raising crime levels.	Destroying millions of acres of U.S. crops, disabling nuclear reactors, and wiping out endangered species.
Number of mentions in the media in the last month, as reported by Google News	"Illegal Immigrants" 20,693	“Invasive Species” 1,291

Photos: www.invasive.org; David McNew/Getty Images