Study shows plant diversity is declining due to success of invasive species

Plant diversity decreases thanks in large part to a global increase in invasive species.

Non-native plant species are spreading faster than ever due to globalization, says Barnabus Daru, Assistant Professor of Biology and Herbarium Curator at Texas A&M-Corpus Christi University. He spoke to Texas Standard about a study he conducted on the causes of plant variety decline. Listen to Daru’s interview in the audio player above or read the transcript below.

This interview has been lightly edited for clarity.

Texas Standard: What are the main factors driving this decline in the variety of plant life?

Barnabou Daru: We are in this biological epoch called the Anthropocene. During this period, we see a huge growth in the human population, the climate is changing so rapidly and species are disappearing at a rapid rate. Species are also being introduced outside their natural ranges beyond historical rates.

So, for this study, we only looked at the last two processes: species extinctions and natural achievements – this is how non-native species are introduced to your ranges. These two processes, together, can combine in what is called “homogenization”, and this means that plant communities become more similar than they were historically.

Could you explain why biological diversity among plant life is important?

This is so important because ultimately our lives, both humans and all other organisms, are linked and intertwined in so many ways. So we depend directly on plants for food, for breathing fresh air, for so many things, like medicine. So if there’s some sort of disconnect – especially because plants are at the beginning of the food chain – then there’s this huge cascading effect on all the other organisms that depend on plants. It is therefore so important that we understand how human activities lead to changes in plant communities because of this and many other reasons.

Is there an example you could cite in Texas where we’re seeing that kind of homogenization?

We have a lot of invasive plants introduced from other parts of the world, including things like King Ranch bluestem which is native to Europe or parts of northern Africa. And they are now being introduced here, and some of the signs of ecological impact are that these grasses tend to form large monocultures that can crowd out native plants. The consequences are that they can destroy the habitats of some native birds like quails and other grassland birds.

Other examples are the Tree of Heaven plant – it is a tree native to central China and Taiwan. One of the ecological impacts of this plant is that it tends to release some sort of chemical around where it grows that suppresses the growth of other plants. So it kind of outshines other native species and hence those native species are not able to thrive.

There are so many examples out there and maintaining the distinctiveness of these plants – particularly because of the benefits we get from them, what they do for the ecosystem, is so vital that we fear losing it at a very fast pace.

Given globalization and given what you have already described, is there anything that can be done to counter this trend at the present time?

There are things that can be done. One of the reasons we conduct our research is to help raise awareness that this is actually happening, as the way species are introduced to new environments can sometimes be intentional or unintentional.

So the first thing we can do is know that this is happening. And the second thing is actually to be very intentional about stopping the intentional reasons or understanding the consequences of what these intentional exchanges are doing. Other ways are to physically remove invasive species as they establish populations in new environments. Many places around the world have programs that actively remove these invasive plants or plants that cause problems in the ecosystem. So these are a few steps that can help stop, or at least minimize, species invasions.

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