Brown rat tops the charts
No, this is not a post about the return of Roland rat to the music industry but a look at the impact of invasive species.
It’s not a nice thought, but in Britain you are never very far from a brown rat. But people living 300 years ago would not have seen this particular species, as it only came to British shores in the 18th century. The brown rat, (Rattus norvegicus), is in fact an invasive species that is not native to Europe, and Swiss scientists have just published a study that concludes that has got the infamous title of the most invasive mammal in Europe.
Invasive species can have many impacts. Their introduction into an ecosystem where they do not belong often results in the decrease of the populations of other native species, and the resulting impact on biodiversity. This might be simply because they prey on these animals, or that they compete, and win, for food or other resources. They may also be the carrier of diseases. One further problem is that can may breed with the native species to cause hybrids.
There is also a severe economic problem to having so many invasive species living in the UK, it is estimated that alien species cost the taxpayer £2 million per year to control. One of the reasons why so much money is being spent is the negative impact that they can have on agriculture.
Looking at invasive species can be useful when teaching about food webs, as students can see how the introduction of a new animal will affect the others in the web. The upd8 activity ‘king crabs’ is a good example of how this can be used.
The point of the scientific study was to get an overall view of what species were causing the most harm to native habitats. They 
used a scorecard approach to assess the impact of the animals they looked at.
This PowerPoint presentation is suitable for GCSE or high level KS3 students and includes a starter to make them think about the impact that invasive species have in the UK. The next slide explains the task, and they can then work in groups to look at the different animals on the next two slides (which can be printed out and cut into cards), in order to give each animal an overall score to find out which of these animals in the UK they would say had the most impact.
Following this, a discussion could be started on what should be done with the information: should the government allocate more money to controlling the ‘top species’, what do we mean by ‘control and monitor’ and should all invasive species be eradicated? You could also look at invasive plant species, and the impact that they can have.
Much of the information I used to write the activity came from this website, which contains a wealth of information on invasive species that could be used in other lessons.
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