Causing Biological Invasion with the Click of a Mouse

Every country is under invasion, not from extra-terrestrial organisms but by native plants from other continents. The case of Switzerland is one such classical example. Long ago Goldenrod, Himalayan balsam and Chinese windmill palm were introduced as ornamental plants and at some point having ‘escaped’ into the wild, they are now threatening the native flora.

The main cause of such biological invasions is global trade, which from the last two decades has shifted to internet and websites such as eBay have become the hub for such transactions. As a consequence, all it takes now is just one click to spread potentially invasive plants from one continent to another.

Monitoring Online Trading

But how big is this online trading in invasive plants? To get an estimate, researchers from ETH Zurich monitored online trade of nearly two thirds of world’s flora on ten online trading platforms including eBay. They picked the list of invasive plants from various conservation bodies including the International Union for the Conservation of Nature (IUCN). This helped them to know whether plant species offered for sale was classified as invasive somewhere else in the world.

For monitoring, they made use of a software which automatically searches the sales platforms and tracks which plant species is being offered for sale in which country and how often. Unfortunately, it was possible only to monitor the supply side, but was not possible to determine whether buyers and sellers in a particular geographic region were actually concluding the business. This was mainly because that information is personal and can be gathered only with the cooperation of the online trading platforms.

Extensive global trading in invasive plants

Despite the limitation, what the software was able to discover surprised the study’s author,

We didn’t expect the global trade in plants that are known to be invasive to be so extensive.

Franziska Humair

In their 50 days of monitoring, researchers spotted 2625 different plant species offered for sale on eBay, which was about 1.4 percent of the seed plants they were seeking for. Out of these, 510 are known to be invasive in one or the other region in the world and 35 of them make the IUCN’s list for the 100 worst invasive species.

The cornflower has become rare in central Europe, but is invading parts of North America. Image credit: H. Zell, CC BY-SA 3.0 / Wikimedia Commons.
The cornflower has become rare in central Europe, but is invading parts of North America. Image credit: H. Zell, CC BY-SA 3.0 / Wikimedia Commons.

Invasive species often up for sale

One of the most often offered plant for sale is the passionfruit, a highly invasive plant in the tropics. It pops-up 90 times in a day, offered by dealers from 17 countries spread across 5 major geographic regions.

Another frequently offered plant is the cornflower. Deemed invasive in certain parts of the USA, it is up for sale more than 80 times a day on average by suppliers located in ten countries spread across five regions.

Interestingly, the plant put up for sale most often is not yet been proven invasive. Desert rose listed for sale on average more than 3100 times a day by dealers from 12 countries, is native to the steppes of Arabia and Africa.

Researchers observed that plant sellers were spread across 65 countries and out of this, offers to sell invasive species came from 55 countries, including Australia.

That was unexpected, since the Australians don’t allow you to bring any invasive plants across their borders. But surprisingly, there are apparently no controls in place to make sure potentially harmful plants don’t leave the continent

Christoph Kueffer, senior lecturer at the Institute of Integrative Biology, ETH Zurich.

Researchers fear that the actual numbers might be much bigger than that found during the study. Researchers monitored the auction for just 50 days and even so, new species turned up for offering every other day. Also, only scientific name of the plant species were used as the search phrase. Researchers believe that, if the common names were also included for search, the numbers could be quite staggering.

The desert rose is the flowering plant offered most frequently for sale online, but is not yet known to be an invasive species. Image source: Wikimedia Commons
The desert rose is the flowering plant offered most frequently for sale online, but is not yet known to be an invasive species. Image source: Wikimedia Commons

Lack of strict rules governing online trade

To put it briefly, the vast majority of invasive species can be easily obtained with just a click of the mouse,
Franziska Humair.

The main reason for the flourishing of this online trade is due to halfhearted implementation of rules governing them. Also, it’s virtually impossible for the dealers themselves to keep track of all the laws and regulations related to invasive species in various countries. Presently, it looks like there is nothing to stem this flourishing trade in invasive species.

With every passing day, the problem is getting aggravated with new threats emerging. Regions like South Africa which previously had no access to trade flows are now participating in this disturbing trade – courtesy of internet.

South Africa is now showing up on our map. We have no idea whether the plants that are being put on the global market from this corner of world will prove to be invasive species The only way to contain invasions is by limiting the trade in potential invaders.

Christoph Kueffer.

The fear is several of them could well become invasive in other geographic regions of the world.

What this study has shown is that, it’s theoretically possible to continuously monitor this trade to pick the newly traded species and avert a possible future biological invasion. Many countries have consciously taken steps to curb the spread of invasive species by implementing new set of rules and regulations governing online trading. Countries like Switzerland has special regulations on the release of certain organisms, and the European Union countries are coming-up with a list of species that are recognized as invaders across the EU.

“As online trade blossoms, it makes it even more urgent for the authorities to take action or for responsible large commercial nurseries to adjust their product ranges,” says Kueffer.


“E-commerce trade in invasive plants”, Franziska Humair et al, Conservation Biology, Vol 29, Issue 6, pages 1658-1665, Dec 2015.

Feature Image: Pretty invasive: passionfruit, is an attractive ornamental plant, native to Brazil, Paraguay and Argentina. Credit, Leonardo Ré Jorge / Wikimedia Commons



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