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Christian Feld on ‘What Can I Do to Help Freshwater Ecosystems?’

August 4, 2016
Red-eared turtles in Lake Baldeney, Essen, Germany. Image: Christian Feld

Red-eared turtles in Lake Baldeney, Essen, Germany. Image: Christian Feld

Last week we began a new series of posts titled ‘What Can I Do to Help Freshwater Ecosystems?‘, in which freshwater experts suggest ways in which the public can help conserve rivers and lakes.  Today we have another post from MARS scientist Christian Feld, which draws on his experiences introduced red-eared turtles to freshwaters around Essen in north-west Germany.


Essen is the centre of a large metropolitan area, called the “Ruhrgebiet” (after the river Ruhr), where around five million people live.

Many of Essen’s inhabitants do not know nature particularly well, often because they haven’t seen too many natural parts of the country. You have to drive an hour at least to see some nice forests. For natural rivers and lakes, you have to drive three hours or more. For many people in Essen this prevents any sort of meaningful interaction with nature.

Now a story: A pet is a pet is a pet

Many children like owning and caring for pets, whether birds, mice, rabbits, turtles. When both pets and children grow older, there is often less enthusiasm to care for the pets. Then, many of these domesticated animals are released in nature.

At Lake Baldeney, south of Essen, we’ve a huge population of red-eared turtle (Trachemys scripta elegans). They come from the Great Lakes in the U.S. and have been introduced to Europe through the pet trade.  They’re sold for €20–30 (only!) and grow up to 50 years. Thus, it is very likely that they won’t live as pets for long, but will be released after a couple of years. Red-eared turtles have spread across the world, and can out-compete native biodiversity for food and habitat, causing significant stress to the health of freshwater ecosystems.

The red-eared turtle is just one example of a freshwater alien species. There are many more – animals as well as plants. They may threaten native biodiversity. They may affect ecosystem’s health and intactness. And finally they may affect us humans.

So what can we do about alien and invasive species? Well, first, we need to take responsibility for our pets. A pet isn’t something you discard after you ‘used’ it for a while. Right now it’s summer time – holiday time. This is the time you may find many more pet animals abandoned or released into nature because they cannot be taken on holidays.

Second, we need to care about alien species. We need to know them and we need to know what they can do to us and our rivers and lakes.

And third, we must respect nature, which gives us so many services and benefits. In general, people shouldn’t interfere with already stressed freshwaters by introducing species that aren’t native to ecosystems. And children should be encouraged to have respectful and inspirational interactions with nature.

This, is what we can do for nature.

4 Comments leave one →
  1. August 4, 2016 14:41

    He Christian I am coming from Essen (currently in Leipzig). I studied biology some time ago and recently again digged into this discipline so I stumbled across your blog.

    I wonder whether there are any reliable insights on the negative/positive effects of the red eared turtle on Essen and its fresh water ecosystems. You only stated there “may” be consequences. Otherwise one consequence is clear: its an additional species so biodiversity increases.

    Another related question: I plan to set up an reef aquarium so I wondered whether and how I should take care to avoid culturing species that have a proven negative track record as invasive species.

    • Christian Feld permalink
      August 22, 2016 13:48

      Dear Johannes, thanks for your comment.

      The red-eared turtle is just one pet species to point at the problem of invasive species being released. I’ve not yet come across scientific studies about positive or negative ecological effects, but this is not the point I wanted to make. Invasive species may have such effects, positive as well as negative, but the fact that we do not know them for sure does not mean they’re harmless. In this regard, the biodiversity argument is tricky.

      Another aspect I’ve not mentioned is the potential threat that the pet trade may constitute for the species in their native environment. But again, the point I wanted to make is: Take care of your (invasive) pets and don’t release them to nature.
      If you want to read more about invasive species in Germany, I’d recommend this site:


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