Most invasive species are introduced into the areas where they become damaging. That’s part of why they tend to be so successful in taking over new environments and causing billions of dollars in damage.

But what if species that we thought were introduced by humans arrived naturally?

In our recent research paper, we made a startling discovery about one of North America’s most ecologically and economically damaging invaders.

The spiny water flea, also known by its scientific names Bythotrephes longimanus and Bythotrephes cederströmii, may have been in North America for centuries longer than believed.

Our finding has implications for how governments and conservation organizations approach invasive species management. Millions of dollars are spent to control the spread of invasive species, but for native species that benefit from environmental change, this strategy may misplace limited funds.

Read more: How the invasive spiny water flea spread across Canada, and what we can do about it

The widely accepted history of the spiny water flea is that it was introduced unintentionally from Europe into Lake Ontario by trans-Atlantic cargo ships in the early 1980s.

In our study, we found reports of the spiny water flea in more than 300 lakes and rivers across Canada and the United States over the past four decades. This number is likely a massive under-estimate because most lakes are not monitored.

Identification of the........

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