A quarter of freshwater animals around the world are at risk of extinction. That’s the finding of a new report published in the journal Nature. While many of those species are found in places like Africa, South America and Asia, there are those in North America, as well — including in Arizona.
Ian Harrison, co-chair of the Freshwater Conservation Committee for the Species Survival Commission and assistant director of the Free-flowing Rivers Lab at Northern Arizona University. He joined The Show to talk more about what he and his colleagues found.
Full conversation
MARK BRODIE: Ian, let's start with the headline here: 1 out of every 4 freshwater animals are at risk of extinction. How concerned and surprised are you by this?
IAN HARRISON: Well, I mean, it's very concerning, definitely that's a very significant, portion of freshwater species that are threatened. I mean, to some extent, not surprising, because we've known for a long time that freshwater species are highly threatened, but to have some, reliable statistic on the extent is, it's good to know. And more importantly, that we actually have this kind of spatially mapped so we can see where globally where the threats are greatest.
BRODIE: Do the places where the threats are the greatest correspond to the places where some of the reasons for this data are coming from? Does that match up where problem and impact?
HARRISON: Well, yes, so, I mean the areas that are heavily threatened where you see gracious numbers of species threatened are ones, to a large extent, where you'd expect that. Whether it's because of habitat loss or overfishing or pollution. So Lake Victoria is in Africa is heavily, heavily threatened, that's a kind of a fishing issue. Parts of India are heavily threatened because of — and that's more a habitat loss issue. So, the areas where you see the large numbers of species threatened, are certainly where, you know, we know that ... there are threats.
BRODIE: What would the impact be of these species actually going extinct? Even if not fully, you know, a quarter of all of them. Let's say some percentage of these species that are threatened to go extinct — what's the impact there?
HARRISON: Well, I mean, from my perspective, obviously the, you know, the first thing is, it's kind of an, an aesthetic loss in that — ... I personally feel that the world is a richer place with the species in it. And so anything that's gone and gone forever is ... is tragic. But there are some very practical reasons — not that that's not practical — but there are very practical reasons for being concerned, in that a loss of a species can affect the ecology of an ecosystem which can then affect other species.
It can create an imbalance in the kind of the food webs, and we've seen that in some lakes where species have been fished out and you get proliferation of other species. So, it causes an ecological disturbance, but also a lot of these species, have an important value to us. You know, obviously fishes, some of them are importantf or fisheries and for subsistence fisheries and for sort of indigenous subsistence fisheries in particular. But there are many other values from freshwater species, beyond food ... Plants are used in many parts of the world for, you know, for thatching, for building huts and things like that. So, there's this, this sort of inherent loss of the ecosystem services they provide.
BRODIE: You mentioned a couple of the places where there are a good number of threatened species. Arizona is not really one of those, although it seems as though you did take a look at a part of the Grand Canyon. And I'm curious what lessons you take from that area and maybe the species in that freshwater body up there, that maybe can teach us something about other places as well?
HARRISON: Yes, well, I mean, if the Grand Canyon is interesting because, yeah, although it's relatively low on numbers of species that are only found there, it means that the threats, proportionally the species that are under threat, are really important because there aren't many species. But they're all heavily threatened. So, that's a significant impact on the ecosystem. And I mean in the case of the Grand Canyon, then we're looking at that issues are caused by river fragmentation, by dams. Which, you know, changing the flows and changing the nature of the water in terms of temperature and things like that — and obviously that's a global issue. I mean there are the issue of dams and fragmentation is global.
But the interesting thing about the Colorado is that you know we've, there are lessons learned from that. There've been great studies from the Global Center — the Grand Canyon Monitoring Center of USGS here —looking at how the changes in flows that affect the macro invertebrates and where they're laying eggs on the rocks. That's affected by the water releases, which reduces invertebrate populations. Which then has a knock-on effect, because there are, you know, birds that live in the canyons that are reliant on those populations. So, bird numbers are, you know, can decline because of that. So it's actually taught us something about the, kind of, the nuances of the ecology of these areas that how one species being impacted can affect many others.
BRODIE: Yeah, that is interesting. So when you look at the places where these species are threatened, is there time to reverse it or? Has the ship kind of sailed on this, do you think?
HARRISON: There is time to reverse it. I mean, I think we have ... a very significant challenge ahead of us, that's for sure. But there is certainly time to reverse this. And I think that's something that this paper is showing, is it's pointing us to where where the the most important areas are. Where we know that there are either the most species that are threatened. Or where, say, there are high numbers of endemic species which are found nowhere else — so, you know, really important to try and conserve them. And it's pointing us to where we can most urgently do work and you know there are solutions in terms about how we think about our water management. And ... how we try and look at, you know, if we're going to do development. You know, where can we do that that's going to be least impactful on ecosystems rather than the most impactful. So definitely there are solutions — challenging ones, but they're there.
BRODIE: Do you find that these tend to be the kinds of solutions that we generally hear about when climate change and that kind of thing comes up, or is this sort of a separate set of changes that we have to make?
HARRISON: I think it it's both. I mean, a lot of them are climate related. I mean then they're becoming more so in terms about how we think about how we're using our water. As I say, if we're thinking about development, then we need to think about what that means in terms of of where we're getting our our water from, and how that impacts the rivers or the lakes or the the underground aquifers that we're taking the water from. I mean, there are other things that that aren't climate related — issues of pollution, for example. Things like that are, are issues that we can address which really aren't aren't climate related but very important. I mean, similarly, the way we use our land, our habitat modification. We can look at that and particularly, you know, how we're managing riparian areas, the forested areas, the vegetation around rivers. Which is really important for them in terms of reducing sediment input and providing shade and and that kind of thing.
