Alien invaders or peaceful co-existors? The matter of non-native species in Britain

By Lilian Halstead

With the world becoming ever more connected, people are not the only things taking advantage of planes and boats to get around. Plant species are constantly being introduced, intentionally or otherwise, into places far outside their original range. The term ‘invasive species’ is sometimes used to refer to any of these non-native species. However, it more usually refers to species that are not native to the country they are growing in but that are able to propagate of their own accord and cause both environmental and economic problems. Not all species that aren’t native are invasive: in fact, it is estimated that out of all the new species arriving by human influence, only ten percent of those will survive in their new environment, and only ten percent of those will go on to have any measurable impact. But if you think of the number of plant species in gardens across the UK, that’s still a substantial number.

Most invasive plants in Britain start off as garden plants that spread to the wild either by releasing seeds or through being dumped as garden waste. Surprisingly, many invasive species are still being sold as garden plants despite their known detrimental effects on biodiversity. Parrot’s Feather is a water plant often sold as an oxygenator for ponds that forms thick mats of vegetation, blocking out light and choking waterways so much that they dramatically increase the risk of flooding. Ironically, Japanese Knotweed, now a notorious invasive species that would cost over £1.5 billion to eliminate from the UK, won a gold medal for being “the most interesting new ornamental plant of the year” when it was first introduced.

So introducing species for gardens can lead to invasive species escaping and causing ecological damage by forming monocultures that shade everything else out, and economic impacts such as exacerbating flooding or growing through tarmac. For this reason there are many schemes that act to monitor the species introduced to see if they become a problem and to hopefully prevent them from doing so in the first place.

But given Britain’s geological past, deciding what is native and what is not is a lot harder than it first appears. Many European species either did not make it into Britain before the English Channel cut Britain off, or went extinct soon afterwards, and humans then subsequently introduced many of them. Species that were introduced by humans a long time ago are known as archeophytes, and one such plant is beech, which was probably introduced 2000 years ago because the nuts are edible. For many species it is hard to tell whether they were there to start with or whether they were introduced. For species that were here once but went extinct before humans arrived, and which were then subsequently reintroduced, it’s not clear whether they should be counted as native or not.

In addition to this, it has to be remembered that ecosystems are not static – succession and evolution are constantly changing the species composition, so trying to exclude species to keep things as they are is sometimes in the best interests of biodiversity, but it isn’t natural. Perhaps hybrid ecosystems altered by non-natives may have their own value, if given the chance to develop properly. Especially if further flow from the source location is halted, then the non-natives may speciate to some degree, which would make them worthy of protection in their own right.

Invasive species are a threat to biodiversity and do need to be controlled if native species are to survive. But the impacts of those that are less damaging can be positive, and given that species transfer is unlikely to stop anytime soon, seeing the value of newly emerging hybrid ecosystems may be a better strategy than attempting to maintain a ‘pure’ state, especially here in Britain, where most of what we think of as natural has been heavily shaped by humanity.

For more information, check out the GB non-native species secretariat, which has a database of most of the invasive species in Britain at the moment.

 

Planet: Why Plants Matter

by Toby McMaster

 

As a world we currently face many major problems, to which we have yet to find specific solutions. The answers to many of these lie, at least partially, in plants. The first land plants appeared roughly 450 million years ago, primates around 80 million years ago and the first Homo sapiens only about 450,000 years ago. In short, for every year humans have inhabited planet Earth, land plants have inhabited it for a millenium. In fact, it seems likely that however hard we try to ruin our planet for ourselves, some vegetation will still outlive us. In the history book of plants, humans may yet just appear as a brief speck – a self-destructive species that got too big for its evolutionary boots and brought entire ecosystems tumbling down with it. Plants are here to stay – so why not use them to try and ensure that we are too? In this first blog entry we will explore the various ways in which plants can help us overcome the issues facing humankind.

Climate Change

With the recent IPCC report on climate change delivering a figure of 95% certainty that humans are causing the current rise in global temperature, it is surely necessary to act to mitigate the situation, even if only as a precaution. Given that 15% of atmospheric CO2passes through plants each year, they are certain to play a role if we are to keep global warming to a minimum. We desperately need a better understanding of the likely worldwide effects of climate change on plant life and to try to work out what we can do to minimise any damage such changes will cause.

Starvation and Malnutrition

According to the World Health Organisation, 842 million people in the world do not have enough to eat. 827 million of these people live in developing countries. The UN predicts that by 2050 the world population will reach 9.6 billion. Moreover that of developed regions is forecast to remain largely unchanged at around 1.3 billion from now until then while the 49 least developed countries are expected to double in size from around 900 million people in 2013 to 1.8 billion in 2050. This will lead to widespread hunger we can’t understand on a scale we can’t understand. These are an intimidating set of circumstances but as a planet we can rise to the challenge. To do this will require improving both crop yields and food distribution, and reducing waste. The fact is that as a massive proportion of the Earth’s ecological base plants represent the most efficient way to feed more people faster. To utilise them we need to explore all the techniques available to us, GM is undoubtedly one of these but is far from a magic bullet, we also need to put as many resources as we can into understanding how to optimise agriculture.

Biodiversity

We are currently in the middle of the 6th mass extinction event in the history of our planet, and the first since 65 million years ago when the dinosaurs were wiped from the face of the Earth. Species are going extinct at somewhere between 100 and 1000 times the expected background rate. It is arguably unethical for our one species to have eliminated so many others, but in one sense extinction is a natural process we have merely accelerated through habitat destruction and climate change. The real issue is that we are reliant on so many species which are in danger of extinction and that we are rapidly losing the opportunities, including novel medicines, offered by so many more.

The approach taken in the past has often been based on the naïve human view that we can just hang on to the species we are interested in and let the remainder of the natural world disappear into oblivion. This is misguided for two main reasons: firstly, our knowledge of the natural world is nowhere near sufficient to rule out species as useless to us, and secondly, species do not exist in isolation but rather as complex ecosytems to be viewed as cohesive units. Plants will represent a massive part of future attempts at restorative ecology – trying to rebuild damaged ecosystems. They must also be carefully protected in the functional ecosystems we still have, as they are so often the foundation stone on which the rest of the community is built.

Medicines

In an age where we have complex techniques such as X-ray crystallography to help probe molecular structures, we might like to think we are beyond simply taking compounds plants have already made for us, and using these chemicals to treat disease. Nothing could be further from the truth. According to the American Association for the Advancement of Science (AAAS) in the year 2000 around 25 percent of prescription drugs dispensed in the United States contain plant extracts or active ingredients derived from plants, and more than 60 percent of cancer drugs on the market were based at least in part on natural products. These are, admittedly, not incredibly recent statistics, but the timescale over which new drug discovery and production takes place means they are likely still approximately accurate. There are still countless conditions and diseases for which we have no or poor treatments, and plants will have a massive role to play in helping fight these ailments.

As demonstrated by the last two examples in particular, these problems are not isolated from each other. Plummeting biodiversity is cutting down our supply of potential new medicines, medicines which we will need to help treat a booming population in developing nations where mortality rates from infectious disease rates are highest. Any new drugs will likely be incredibly expensive to begin with, a problem which may be compounded by the economic impact of climate change on developing countries.

This is only a short list of the problems we face and plants may well not hold the solution to all of them, but they are an incredible natural resource which we should make use of. This blog is dedicated to discussing the ways in which we can do this, and to generating enthusiasm for plant science research.