Extinctions linked to wildlife trade

Thousands of species of animals, plants and fungi are traded internationally. And as human pressure on the environment intensifies, and the relentless drive for economic growth increases, some species are - unsurprisingly - buckling under the strain. But how many? The answer is that we don’t really know, so Oxford University’s Amy Hinsley, speaking to Chris Smith, decided to try to find out by mining the literature for reports on species driven to extinction by trade. She found at least 511 taxa extinctions, but it’s likely this is very much the tip of the iceberg…

Amy - People often say that wildlife trade is a really big threat to wild species, and people often talk about it as a major driver of extinction. But we hadn't seen any evidence of how many extinctions there had been linked to wildlife trade. We didn't know where these claims were coming from, whether there were recorded examples of extinctions linked to trade, or how many there were, what kind of extinctions were happening, whether it was complete global extinctions or local extinctions. So we really wanted to know what the actual evidence was.

Chris - I suppose there's two sides to the coin as well, isn't there? Because it's not just a one-way street bad news. You trade in something and it goes extinct because there are some things which are safeguarded and cherished because we trade in them and so therefore they're gonna get conserved and preserved.

Amy - Yes. Wildlife trade can sometimes be portrayed as a purely negative thing. It's often discussed in terms of illegal wildlife trade or over harvesting, but wildlife trades is happening globally on lots of different scales from people collecting things from the wild and selling them in local markets to people exporting plants and animals and fungi internationally in legal markets and sustainably. There's lots of evidence that wildlife trade in certain species, if done well and managed well, can be sustainable. It can support livelihoods, it can support economies. Obviously there can be negative impacts of wildlife trade if over-harvesting takes place or if the management of things like where people are harvesting or what parts of a plant, for example, people are harvesting. But it's really important to acknowledge from this that wildlife trade is not always a negative process and it can also lead, like you say, towards people valuing species more. It can lead to better protections for species in the wild, when it is done in a well-managed and legal sustainable way.

Chris - How well documented is all of this then? Where did you begin?

Amy - The conservation status of many species has been assessed by the International Union for the Conservation of Nature or IUCN. So we looked at the redlist data to see whether any of the species that are noted as extinct or extinct in the wild by the redlist had any links between that extinction and any kind of trade. But we also know that lots of species are not assessed by the redlist process. So plants, for example, fungi, very few species overall have been assessed by the redlist. So we also looked in the academic literature. So we did structured searches. We used keywords such as "trade" or "over-harvest" and "extinction". And we combined these keywords to try and find as many papers as possible that referred to extinction and the trade. And then we went through all those papers. It took a very long time. There were more than a thousand papers and we looked for concrete examples where people had reported that a species had gone extinct. And when we're talking about extinct, we might be talking about global extinction where the species has not been found again in the wild extinction in the wild where it is known from cultivation, but it no longer exists in the wild, or local extinction where it has disappeared from a certain area, but it still exists in other areas.

Chris - There's going to be a lot of ice under the waterline of this iceberg, isn't there in the sense that there will be things that just haven't been studied. There will also be things that are not explicitly referred to as extinct. They may have used other terms like "lost" or "disappearance", which means you wouldn't spot them with this analysis. So this is very much tip of the iceberg stuff.

Amy - Yes. And I think there are are three main ways that this should be considered as an underestimate. Somebody might have reported an extinction, but used words such as this species has disappeared from the wild, this species has been lost. They might have thought it was extinct but not really have the evidence for that, so they might have said that it had declined and not been found. What was quite striking for me in the results was that we had lots of examples of animal extinctions. Very, very few of plant extinctions, and only one example of a fungal species going extinct. So there's also the problem of under-researched and overlooked groups. So there could just be a lot of species out there going extinct that we don't know about. And, finally, extinction is a very complex process. So lots of different things could contribute to extinction. So there could be extinctions out there in traded species where trade was the main driver of extinction, but that's not known or it's not being investigated. So the links between trade and extinction have not been made.

Chris - There's also potentially a domino effect isn't there in the sense that say I trade in species A, and species A is the food for species B and I drive species A to extinction because I overexploit it, then I've also indirectly caused the potential extinction or endangerment of species B because I've deprived it of what it would normally eat. But I wouldn't be monitoring species B, or writing about it, so we wouldn't know about that extinction.

Amy - Yes, and And I actually think the indirect effects of trade on a wild population or a wild species are potentially driving some species to extinction. And that includes harvesting of all of a prey species, for example, or introduction of a species for commercial trade that then becomes a predator of natural species in that area. So one of the main examples, fish species, which had gone extinct due to the introduction of the Nile perch, which was used in commercial fisheries, but then ate all of the native species in those lakes. So I think it was around 200 species went extinct due to that. And that is an indirect effect, and that was recorded in the literature. But there might have been other examples out there that didn't record trade as a driver.