This is a fascinating article about a fascinating topic. Perhaps clarifying and simplifying some of the specific issues that lead to "introduced" plants/animals having a negative affect on biodiversity would be the way to shift the issue away from blanket negativity and consequent protectionism?
One example: both Red Oak and Hungarian Oak outcompete the English Oak in e.g. Richmond Park, and that this has a negative affect on biodiversity because they only host about 1,000 of the 4,000 species that rely on Pedunculate oak. However, introduction of other oak species (e.g. Quercus brantii from Iraq), particularly as street trees, will almost certainly have a positive effect on biodiversity, because they can grow in drought-affected areas where Pedunculate oak could not. Frame this as an "outcompeting species" and a "resilient species" in everyday discourse and the conversation may become less loaded?
Disputing biotic nativeness is a convenient way to exculpate human agency in homogenising the biota of the planet. Shouldn’t we be “asking” wild nature what it thinks of this homogenisation? Rhetorical question, but in the absence of being able to do that, the next best thing is to recognise and honour the distinctiveness, endemism and biogeographical distribution due to the intrinsic boundaries to movement ecology that characterises the species of wild nature.
There may be hope that through reversing landscape simplification, by refilling native trophic levels, that biological systems may be self-rectifying – the pine marten and grey squirrel would be one example. In some places, it is a messy, additive chain of non-natives: the trophic ecology of Australia – its small native mammals and endemic vegetation - is destroyed by non-natives (red fox, rabbit) but with the hope that the dingo, a feral dog, can replace the extinct apex predator, the thylacine. It will not work everywhere – some trophic imbalances created by human agency, particularly on islands, can only be solved by removal. Do we not bother?
Your opinion is deeply rooted in misinformation and on a disturbing lack of understanding of how ecosystems function. Advocate for changes in the way immigrants are treated, for changes on how they are addressed, fight for the proper and inclusive language to cull racism. Do not undermine the fight against biodiversity loss. Non-native species are one of the major threats to biodiversity and we must fight them. Strong words are necessary, especially if coupled with strong actions. There is nothing to do with a sense of purity. These words have nothing to do with race. It's the other way around. Stop mixing social and ecological questions that you clearly do not fully understand. Please, do not dissiminate more misinformation. We need more people working towards a healthy and biodiverse world with structurarly and naturally sound ecosystems. We can't cope with more impoverished and non-functional ecosystems. You are being a part of the problem and that is very worrying and saddens me.
What a thought provoking article, it's certainly made me reconsider the language I use (I am a scientist who has written reports and papers on "non-native" species in the past) and the underlying biases I may have, despite my best efforts to be inclusive and anti-racist. I like the idea of using "introduced" instead of "non-native". Not only is it a gentler and less inflammatory term, it also more accurately describes the range of issues we are trying to deal with in relation to introduced species (to take an example from your article, think hedgehogs in the Hebrides - they are a native species to the UK, so they could not be accurately described as "non-native". The issues we are trying to deal with in relation to problematic introduced species do not relate to national boundaries).
'Introduced' is good substitute for 'non-native' in many cases. I feel it falls short as an all-encompassing alternative as 'introduced' implies intent, yet many 'introductions' are accidental and/or an indirect result of human influence on ecosystems - eg new arrivals due to anthropogenic climate change. As you point out, an introduced species can also be a native species at certain spatial scales. It is hard to come up with an adequate alternative to 'non-native' that does not explicitly distinguish between a species that is 'of this place' and a species 'not of this place' because that is the fundamental distinction we need to make when looking at evolution, interaction and resilience.
Good point about the "native" hedgehog becoming a problem when "introduced" to the Hebrides. Any species can become a problem when it is introduced to the wrong place. This is why the debate should use careful language and be precise. And more easy then, to demonstrate that the matter has absolutely nothing to do with the movement of human beings. Humans are all the same species, after all.
I feel it is important to point out that the term 'non-native' is a little more multi-dimensional than is suggested here. It relates to more than simply the 'foreign-ness' of a species or its' potential to change/disrupt its adopted ecosystem. Additionally and perhaps most importantly, the term 'non-native' is primarily a way of distinguishing a species which has evolved autonomously within it's surrounding vegetative habitat, usually over thousands of years on any given landmass, and not wittingly or unwittingly introduced by humans.
.
It is important to make this distinction for two reasons - one in order to define the progression of evolution of species and ecosystems and two because it separates the organic from the anthropogenic.
You rightly say there was no 'Eden' and the evolution and distribution of species has always been fluid. Biologists are naturally acutely aware of the movement of species through time, yet they don't think of the hippopotamus as being 'native' to Britain despite the fact they well know that hippos wallowed peacefully in the vicinity of the Thames tens of thousands of years before the first fox or badger ran through an oakwood.
Why? Well, the only reason species survive on Earth over millions of years of perpetual environmental change is through evolving resilience. Resilience requires the ability to sustain populations long term, to migrate, to maintain genetic diversity and to adapt to environmental
change. This resilience is built up by individual species via evolutionary processes and movements which usually occur over many thousands of years.
Hippos were not resilient to the long-term climate patterns in western Europe. Thus they became extinct from there, but over thousands of years. It generally takes a species a long time to establish or become extinct in nature - by contrast humans rapidly assist the establishment and the extirpation of species all over the world - with highly varied, unpredictable and mostly unknown short and long-term results. This is why the separation of 'native' and 'non-native' is so important in ecology and will remain so as we aim to more deeply understand plant-species interactions and preserve long-established ecosystem and species resilience.
Ultimately, the term 'non-native' is applied by ecologists to plants and animals - not to 'people'. Not ignoring that 'people' are animals, but interestingly, we human animals are, by all current scientific definitions of 'native', ecologically native to everywhere. We were all over the planet during at least two glaciations, several floods and at least one major eruption/meteor strike or two. We have naturally evolved in multiple ecosystem environments around the world through various great environmental changes.
With this in mind it seems somewhat paradoxical that biological terms such as 'non-native', which could not scientifically and accurately be applied to humans, should be offensive to humans. The offence is only possible when applying strictly cultural meanings to such terms, meanings that derive from human cultural constructs of 'nation' and 'race'. These cultural constructs have long divided humans, yet they are abstracts, not things that exist in tangible objective reality - which is what science mainly deals with. Perhaps a better term than 'non'native' is needed in ecology, IF a satisfactory and scientifically robust term can be found. Or, perhaps we should spend our contemplation more on what the science behind the term means to us all equally as human animals, as opposed to concerning ourselves with what the cultural loadedness of the term means to some of us unequally as individual humans.
Perhaps detaching our cultural selves from sensibilities about words, at least where ecology is concerned, and focusing instead on the fine detail of the ecological concepts those words are utilised to represent, can nurture more perspective from the human-animal worldview. This was, after all, our first worldview, a shared worldview that many have lost touch with, in which we
humans are an interactive part of a huge ecosystem of plants and creatures where race and nationality have little currency and are far less able to permeate the collective consciousness and exert influence.
As an aside, there is definitely an SEO incentive for publications to use certain inflammatory words in reporting on these creatures (particularly "alien", for reasons unrelated to biodiversity).
There are two issues here but they are clearly related. First the harm (or not) that introduced species can do, and secondly the issue of language. I wonder if we are simply overthinking the language issue. I see no problem when discussing wildlife in using terms that would be entirely inappropriate for humans. It is entirely legitimate to talk of a 'non-native' species, decide if it is likely to be 'harmful' and 'invasive', and decide, if necessary, to 'eradicate' it. Of course, none of that language is ever appropriate for humans in a multicultural society. Equally, swatting a fly is not 'murder', and the well-publicised cull of Ruddy Ducks was not 'ethnic cleansing'. These words relate very specifically to actions against humans and cannot simply be co-opted for other animals.
I fear that this issue over language has been largely contrived by those opposed to the control of non-natives in order to blur the issues. Much as animal rights groups have suggested ‘meat is murder’, those opposed to culls of non-natives have sought to use deliberately provocative and inflammatory language to draw parallels with abhorrent actions against humans in order to build support – hence ‘ethnic cleansing’.
I remain unconvinced that the terms mentioned in this piece are upsetting for ethnic minorities when they are applied to wild animals and plants. But that is not for me to say and it would be interesting to learn more about this. If the language IS causing a problem and we need to revisit it then we'll need a whole suite of new terms to cover all the actions that are so essential in identifying problematic non-native species and their effective control. The piece suggests ‘introduced’ for ‘non-native’ which is fine – but what about all the other terms?
Interestingly it may also be about narative and perspectives - for instance H.Balsam considered an invasive weed. If you look more closely perhaps its expansion is merely a reaction to hman behaviour. See
The terms "introduced" and "introduction" can be used if allochthonous is too unwieldy. The fact that ecologists go to great lengths to control native invasive species shows that it is the invasiveness that is considered the problem, not the non-nativeness. Indeed, if a species arrives of its own accord, such as the collared dove, it is usually considered native, or a natural colonist, and is generally welcomed by ecologists and other naturalists. The hoverfly Volucella zonaria is another example. We need to base our plans and actions on science but we can take care over the language we use. Thank you Sophie for an interesting summary of the matter.
Non-native may be an issue to be addressed* but I would have thought that the more important issue is being invasive. And that being invasive has come about through man's activities, whether that be deliberate importation or inadvertent in imported goods, or even change of practice which allows a plant to become invasive. Isn't it the case that both 'native' or 'non-native' can be invasive - I would think bracken is an example in the Lake District?
*personally in relation to plants I don't think the native/non-native terminology is an issue. I find it factual and descriptive, and feel capable of distinguishing this from when we are talking about people.
this Wednesday 15th of July, 14.00 hrs CET-1 / uk time I organise a webinar on Japanese Knotweed: alien plants have increased bio-diversity. You are very welcome to participate: if you send a mail to catherinevanolden@gmail.com I will send you a link to enter the Webinar. Best wishes, Catherine will send you seperately the invite
Really interesting article - thank you Sophie. I think that in all fields of study, professions, life in general we have to acknowledge that language can be emotionally loaded and that just sitting back on the notion that by using an 'accepted' scientific term a particular word or phrase is removed from being emotionally charged may ignore the wider issues. I like the suggestion of ‘introduced’ instead of ‘non-native’, and really don’t see an issue with us re-examining our use of language when issues such as those raised in yours and Claire’s articles are raised. If that re-examination also stimulates debate on the subject matter (for example levels of control on introduced species) then that’s good isn’t it, that’s how we develop and move forward, by constantly questioning what we assume?
"non-native plants are often regarded, unquestioningly, as inferior"
This is indeed true, but the more you DO question this the more you find that from an ecological perspective non-native/introduced plant species (particularly those from outside western Europe) are vastly inferior as sources of pollen, nectar and leafy sustenance for native/non-introduced pollinators and other insects.
Clearly the parallels drawn between how incoming peoples and incoming species are treated are uncomfortable and just saying, 'understand ecology more' or 'don't read too much into it' are not going to fix this, but then I am not sure that changing the terminology fixes this either.
But what about Harriet Rix's point below, that there are cases where introduced plants can improve biodiversity, or indeed Mark Fisher, who points out that non-native introductions can replace lost species and improve ecosystems? I think that speaking in absolutes – one positive, the other negative – is an imprecise way of thinking about the issue, and the language around the subject reinforces this.
(And surely this topic is also complicated by climate change, as some native species become less adapted to the current environment, whereas introduced species will thrive.)
Indeed, but I don't see anyone actually arguing that all non-native species are bad, I have successfully campaigned to get the Roman snail on the UK list of protected species because it is on continental concern, despite UK populations being non-native - I would argue that we should similarly value the population of Nobel crayfish. My point above alludes to the fact that the associations of species in Western Europe have been broken and reformed many times over the last few hundred years as climate has changed, old acquaintances, and I suspect less likely to harbour unmitigated disease or to devastate native populations, as the Asian Harlequin ladybird has done to several species of native ladybird in Europe and America.
That point depends on species richness at any point in space being the most appropriate measure of biodiversity, it's more complex than that. Some of the most special habitats have very few species, but those species can survive almost nowhere else - for instance coastal shingle habitats - you would not plant Dungeness with Turkey oak because while you would definitely increase species richness at the site level, you would reduce it at a UK level and damage genetic diversity at a global level.
And that's a perfect illustration of why favouring native species (for no other reason than the fact they are native) as well as allowing natural processes to play out (where possible) is entirely justifiable. Humans can always add more and more introduced species by releasing or planting them but it doesn't make for good conservation.
A technical term for a non-native species or population, that comes without any emotional loading, is allochthonous. A population that got here by itself and maintains itself without human intervention can be described as autochthonous, and allochthonous is its antonym. Yes, these are obscure and overtly scientific terms but surely the debate should be based on science? Thank you for a timely and thoughtful essay, Sophie.
This is a fascinating article about a fascinating topic. Perhaps clarifying and simplifying some of the specific issues that lead to "introduced" plants/animals having a negative affect on biodiversity would be the way to shift the issue away from blanket negativity and consequent protectionism?
One example: both Red Oak and Hungarian Oak outcompete the English Oak in e.g. Richmond Park, and that this has a negative affect on biodiversity because they only host about 1,000 of the 4,000 species that rely on Pedunculate oak. However, introduction of other oak species (e.g. Quercus brantii from Iraq), particularly as street trees, will almost certainly have a positive effect on biodiversity, because they can grow in drought-affected areas where Pedunculate oak could not. Frame this as an "outcompeting species" and a "resilient species" in everyday discourse and the conversation may become less loaded?
Disputing biotic nativeness is a convenient way to exculpate human agency in homogenising the biota of the planet. Shouldn’t we be “asking” wild nature what it thinks of this homogenisation? Rhetorical question, but in the absence of being able to do that, the next best thing is to recognise and honour the distinctiveness, endemism and biogeographical distribution due to the intrinsic boundaries to movement ecology that characterises the species of wild nature.
There may be hope that through reversing landscape simplification, by refilling native trophic levels, that biological systems may be self-rectifying – the pine marten and grey squirrel would be one example. In some places, it is a messy, additive chain of non-natives: the trophic ecology of Australia – its small native mammals and endemic vegetation - is destroyed by non-natives (red fox, rabbit) but with the hope that the dingo, a feral dog, can replace the extinct apex predator, the thylacine. It will not work everywhere – some trophic imbalances created by human agency, particularly on islands, can only be solved by removal. Do we not bother?
Your opinion is deeply rooted in misinformation and on a disturbing lack of understanding of how ecosystems function. Advocate for changes in the way immigrants are treated, for changes on how they are addressed, fight for the proper and inclusive language to cull racism. Do not undermine the fight against biodiversity loss. Non-native species are one of the major threats to biodiversity and we must fight them. Strong words are necessary, especially if coupled with strong actions. There is nothing to do with a sense of purity. These words have nothing to do with race. It's the other way around. Stop mixing social and ecological questions that you clearly do not fully understand. Please, do not dissiminate more misinformation. We need more people working towards a healthy and biodiverse world with structurarly and naturally sound ecosystems. We can't cope with more impoverished and non-functional ecosystems. You are being a part of the problem and that is very worrying and saddens me.
What a thought provoking article, it's certainly made me reconsider the language I use (I am a scientist who has written reports and papers on "non-native" species in the past) and the underlying biases I may have, despite my best efforts to be inclusive and anti-racist. I like the idea of using "introduced" instead of "non-native". Not only is it a gentler and less inflammatory term, it also more accurately describes the range of issues we are trying to deal with in relation to introduced species (to take an example from your article, think hedgehogs in the Hebrides - they are a native species to the UK, so they could not be accurately described as "non-native". The issues we are trying to deal with in relation to problematic introduced species do not relate to national boundaries).
'Introduced' is good substitute for 'non-native' in many cases. I feel it falls short as an all-encompassing alternative as 'introduced' implies intent, yet many 'introductions' are accidental and/or an indirect result of human influence on ecosystems - eg new arrivals due to anthropogenic climate change. As you point out, an introduced species can also be a native species at certain spatial scales. It is hard to come up with an adequate alternative to 'non-native' that does not explicitly distinguish between a species that is 'of this place' and a species 'not of this place' because that is the fundamental distinction we need to make when looking at evolution, interaction and resilience.
Good point about the "native" hedgehog becoming a problem when "introduced" to the Hebrides. Any species can become a problem when it is introduced to the wrong place. This is why the debate should use careful language and be precise. And more easy then, to demonstrate that the matter has absolutely nothing to do with the movement of human beings. Humans are all the same species, after all.
I feel it is important to point out that the term 'non-native' is a little more multi-dimensional than is suggested here. It relates to more than simply the 'foreign-ness' of a species or its' potential to change/disrupt its adopted ecosystem. Additionally and perhaps most importantly, the term 'non-native' is primarily a way of distinguishing a species which has evolved autonomously within it's surrounding vegetative habitat, usually over thousands of years on any given landmass, and not wittingly or unwittingly introduced by humans.
.
It is important to make this distinction for two reasons - one in order to define the progression of evolution of species and ecosystems and two because it separates the organic from the anthropogenic.
You rightly say there was no 'Eden' and the evolution and distribution of species has always been fluid. Biologists are naturally acutely aware of the movement of species through time, yet they don't think of the hippopotamus as being 'native' to Britain despite the fact they well know that hippos wallowed peacefully in the vicinity of the Thames tens of thousands of years before the first fox or badger ran through an oakwood.
Why? Well, the only reason species survive on Earth over millions of years of perpetual environmental change is through evolving resilience. Resilience requires the ability to sustain populations long term, to migrate, to maintain genetic diversity and to adapt to environmental
change. This resilience is built up by individual species via evolutionary processes and movements which usually occur over many thousands of years.
Hippos were not resilient to the long-term climate patterns in western Europe. Thus they became extinct from there, but over thousands of years. It generally takes a species a long time to establish or become extinct in nature - by contrast humans rapidly assist the establishment and the extirpation of species all over the world - with highly varied, unpredictable and mostly unknown short and long-term results. This is why the separation of 'native' and 'non-native' is so important in ecology and will remain so as we aim to more deeply understand plant-species interactions and preserve long-established ecosystem and species resilience.
Ultimately, the term 'non-native' is applied by ecologists to plants and animals - not to 'people'. Not ignoring that 'people' are animals, but interestingly, we human animals are, by all current scientific definitions of 'native', ecologically native to everywhere. We were all over the planet during at least two glaciations, several floods and at least one major eruption/meteor strike or two. We have naturally evolved in multiple ecosystem environments around the world through various great environmental changes.
With this in mind it seems somewhat paradoxical that biological terms such as 'non-native', which could not scientifically and accurately be applied to humans, should be offensive to humans. The offence is only possible when applying strictly cultural meanings to such terms, meanings that derive from human cultural constructs of 'nation' and 'race'. These cultural constructs have long divided humans, yet they are abstracts, not things that exist in tangible objective reality - which is what science mainly deals with. Perhaps a better term than 'non'native' is needed in ecology, IF a satisfactory and scientifically robust term can be found. Or, perhaps we should spend our contemplation more on what the science behind the term means to us all equally as human animals, as opposed to concerning ourselves with what the cultural loadedness of the term means to some of us unequally as individual humans.
Perhaps detaching our cultural selves from sensibilities about words, at least where ecology is concerned, and focusing instead on the fine detail of the ecological concepts those words are utilised to represent, can nurture more perspective from the human-animal worldview. This was, after all, our first worldview, a shared worldview that many have lost touch with, in which we
humans are an interactive part of a huge ecosystem of plants and creatures where race and nationality have little currency and are far less able to permeate the collective consciousness and exert influence.
As an aside, there is definitely an SEO incentive for publications to use certain inflammatory words in reporting on these creatures (particularly "alien", for reasons unrelated to biodiversity).
There are two issues here but they are clearly related. First the harm (or not) that introduced species can do, and secondly the issue of language. I wonder if we are simply overthinking the language issue. I see no problem when discussing wildlife in using terms that would be entirely inappropriate for humans. It is entirely legitimate to talk of a 'non-native' species, decide if it is likely to be 'harmful' and 'invasive', and decide, if necessary, to 'eradicate' it. Of course, none of that language is ever appropriate for humans in a multicultural society. Equally, swatting a fly is not 'murder', and the well-publicised cull of Ruddy Ducks was not 'ethnic cleansing'. These words relate very specifically to actions against humans and cannot simply be co-opted for other animals.
I fear that this issue over language has been largely contrived by those opposed to the control of non-natives in order to blur the issues. Much as animal rights groups have suggested ‘meat is murder’, those opposed to culls of non-natives have sought to use deliberately provocative and inflammatory language to draw parallels with abhorrent actions against humans in order to build support – hence ‘ethnic cleansing’.
I remain unconvinced that the terms mentioned in this piece are upsetting for ethnic minorities when they are applied to wild animals and plants. But that is not for me to say and it would be interesting to learn more about this. If the language IS causing a problem and we need to revisit it then we'll need a whole suite of new terms to cover all the actions that are so essential in identifying problematic non-native species and their effective control. The piece suggests ‘introduced’ for ‘non-native’ which is fine – but what about all the other terms?
rhododendron NON-native species !!!!!
Interesting article.
Interestingly it may also be about narative and perspectives - for instance H.Balsam considered an invasive weed. If you look more closely perhaps its expansion is merely a reaction to hman behaviour. See
An interesting recent UK/swiss study stating "Conclusions The findings from both rivers led us to rethink our original hypothesis; that HB promotes soil erosion, to an amended hypothesis in which HB may be associated with areas where high erosion is sometimes recorded." (https://www.researchgate.net/publication/325565991_The_invasive_alien_plant_Impatiens_glandulifera_Himalayan_Balsam_and_increased_soil_erosion_causation_or_association_Case_studies_from_a_river_system_in_Switzerland_and_the_UK)
Implying that the soil was already degraded (presumably by human behavior). It seems unfair and illogical to
blame the plant.
The terms "introduced" and "introduction" can be used if allochthonous is too unwieldy. The fact that ecologists go to great lengths to control native invasive species shows that it is the invasiveness that is considered the problem, not the non-nativeness. Indeed, if a species arrives of its own accord, such as the collared dove, it is usually considered native, or a natural colonist, and is generally welcomed by ecologists and other naturalists. The hoverfly Volucella zonaria is another example. We need to base our plans and actions on science but we can take care over the language we use. Thank you Sophie for an interesting summary of the matter.
Non-native may be an issue to be addressed* but I would have thought that the more important issue is being invasive. And that being invasive has come about through man's activities, whether that be deliberate importation or inadvertent in imported goods, or even change of practice which allows a plant to become invasive. Isn't it the case that both 'native' or 'non-native' can be invasive - I would think bracken is an example in the Lake District?
*personally in relation to plants I don't think the native/non-native terminology is an issue. I find it factual and descriptive, and feel capable of distinguishing this from when we are talking about people.
this Wednesday 15th of July, 14.00 hrs CET-1 / uk time I organise a webinar on Japanese Knotweed: alien plants have increased bio-diversity. You are very welcome to participate: if you send a mail to catherinevanolden@gmail.com I will send you a link to enter the Webinar. Best wishes, Catherine will send you seperately the invite
Really interesting article - thank you Sophie. I think that in all fields of study, professions, life in general we have to acknowledge that language can be emotionally loaded and that just sitting back on the notion that by using an 'accepted' scientific term a particular word or phrase is removed from being emotionally charged may ignore the wider issues. I like the suggestion of ‘introduced’ instead of ‘non-native’, and really don’t see an issue with us re-examining our use of language when issues such as those raised in yours and Claire’s articles are raised. If that re-examination also stimulates debate on the subject matter (for example levels of control on introduced species) then that’s good isn’t it, that’s how we develop and move forward, by constantly questioning what we assume?
"non-native plants are often regarded, unquestioningly, as inferior"
This is indeed true, but the more you DO question this the more you find that from an ecological perspective non-native/introduced plant species (particularly those from outside western Europe) are vastly inferior as sources of pollen, nectar and leafy sustenance for native/non-introduced pollinators and other insects.
Clearly the parallels drawn between how incoming peoples and incoming species are treated are uncomfortable and just saying, 'understand ecology more' or 'don't read too much into it' are not going to fix this, but then I am not sure that changing the terminology fixes this either.
But what about Harriet Rix's point below, that there are cases where introduced plants can improve biodiversity, or indeed Mark Fisher, who points out that non-native introductions can replace lost species and improve ecosystems? I think that speaking in absolutes – one positive, the other negative – is an imprecise way of thinking about the issue, and the language around the subject reinforces this.
(And surely this topic is also complicated by climate change, as some native species become less adapted to the current environment, whereas introduced species will thrive.)
Indeed, but I don't see anyone actually arguing that all non-native species are bad, I have successfully campaigned to get the Roman snail on the UK list of protected species because it is on continental concern, despite UK populations being non-native - I would argue that we should similarly value the population of Nobel crayfish. My point above alludes to the fact that the associations of species in Western Europe have been broken and reformed many times over the last few hundred years as climate has changed, old acquaintances, and I suspect less likely to harbour unmitigated disease or to devastate native populations, as the Asian Harlequin ladybird has done to several species of native ladybird in Europe and America.
That point depends on species richness at any point in space being the most appropriate measure of biodiversity, it's more complex than that. Some of the most special habitats have very few species, but those species can survive almost nowhere else - for instance coastal shingle habitats - you would not plant Dungeness with Turkey oak because while you would definitely increase species richness at the site level, you would reduce it at a UK level and damage genetic diversity at a global level.
And that's a perfect illustration of why favouring native species (for no other reason than the fact they are native) as well as allowing natural processes to play out (where possible) is entirely justifiable. Humans can always add more and more introduced species by releasing or planting them but it doesn't make for good conservation.
A technical term for a non-native species or population, that comes without any emotional loading, is allochthonous. A population that got here by itself and maintains itself without human intervention can be described as autochthonous, and allochthonous is its antonym. Yes, these are obscure and overtly scientific terms but surely the debate should be based on science? Thank you for a timely and thoughtful essay, Sophie.
Perhaps that could be a solution! If only those words were easier to spell... :)