Q: Last week we learnt that Jurassic-era cycads are set to reproduce amid unprecedented heating in the UK. What obvious stories of heating is South African biodiversity giving us?
A: In the early 2000s, I worked with my colleague [conservation biologist] Wendy Foden to study the quiver tree, which we chose for its visibility in surrounding vegetation, the fact that its skeleton stays standing as evidence of mortality, as well as its huge geographic range extending from Nieuwoudtville, a little north of Cape Town, all the way up to Brandberg in Namibia. Wendy showed there was much higher mortality in warmer parts of the quiver tree’s geographic range extending from the Gariep Basin towards Namibia.
In the south, near Nieuwoudtville, its population was expanding like mad, with a huge increase in juveniles and recently established individuals. We concluded that its range might even be able to shift towards the south into areas where it appears not to have existed before. Sometimes called the “fingerprint of climate change”, these are typical signs of a species range responding to climate. The heat and drought in the north exceed its survival capacity and, in the south, where its growth is historically limited by lower temperature, warming accelerates growth. This is an ongoing study, and this work and our conclusions have been academically challenged, but we remain of the view that the balance of evidence suggests the species is responding to climate change.
Q: As the author of South Africa’s first national climate reports, you have a view of global change science that spans decades. What do the trends tell us about the relationship between wildfire and the climate crisis?
A: We should expect significant impacts on species and ecosystems. That’s still my position. But we can’t ascribe the observed increasing frequency of fires in fynbos to climate change, because people starting fires or accidental fires play a big role in influencing that signal.
As shown by a student I co-supervised, Diane Southey, in her beautiful master’s thesis at the University of Cape Town, what we do appear to be seeing in fynbos is a greater frequency of big, damaging fires — like the one that took out large areas of Knysna. This phenomenon seems to be related to the increasing occurrence of climatic conditions that drive big fires. Sometimes called “30:30:30” conditions as one of these useful rules of thumb, these conditions are winds in excess of 30km/h, temperatures in excess of 30ºC and humidity lower than 30%. Put that mix together and you have a fire that becomes almost impossible to control.
Over in Australia, there’s been an increase in very significant fires, to such an extent that Australians created a new fire-risk category after the 2009 “Black Saturday” fires in Victoria. This is the so-called “code red” or catastrophic-fire danger rating, on top of the old “extreme” risk category. They’d be horrified at our lax controls of people’s use of fire here in the Cape. I’ve even seen reports that the koala bear is functionally extinct by some definitions, existing in smaller populations as their habitats are threatened by heatwaves, droughts and the risk of fire. They’re also affected by disease probably unrelated to climate change. So, Australians are extremely interested in fire and they’ve had the incentive to develop a much better ability to model the dynamics of it. They’re way ahead of South Africans in terms of this. We have some catching up to do here.
Q: We know that the Amazon fires are a result of industrial-complex conflict. But are these big, damaging fires in Australia a result of the climate crisis?
A: Yup, absolutely.
Q: Have there been big shake-ups to your work over the past decade or two, forcing you to return to the drawing board?
A: We’ve had to engage with just how much resilience of different kinds there is in nature. For example, in mountain areas or areas of high topographic diversity, you have a lot of micro-climates where species may hang out, even though the broader area may become too warm. They may be able to survive in a little kloofie, or on some south-facing slope. Even though the conditions should be exceeded for them and they should be absent, you might still find them in these refugia.
Q: Given all this uncertainty, have southern African biodiversity scientists contributed any irrefutable evidence to global climate change knowledge?
A: We’ve added 40% more CO2 since the Industrial Revolution. That’s a huge increase in CO2 and we have irrefutable evidence that there’s been a lot of bush encroachment over vast areas of southern Africa. At least part of that pattern can be attributed to rising CO2. In fact, we’ve done some of the only work in the world on this effect in savanna systems, by showing that rising CO2 acts as an aerial fertiliser for some savanna trees and, possibly, for nitrogen-fixing trees like our acacias especially. This boosts the growth of establishing individuals — young seedlings and saplings. Our research shows this has very likely contributed to the problem of bush encroachment in areas like the Eastern Cape, KwaZulu-Natal and possibly a whole bunch of southern African ecosystems. CO2 definitely has an impact. We’ve done the experiments that show this. We’ve done the modelling that simulates it and the observations tend to back it up.
Q: So, we’re hardly looking at southern Africa turning into one massive homogeneous desert?
A: Not at all, the picture is much more complex. Over the past decade, we’ve extensively published a more detailed, nuanced view of what significant change we might expect, which includes some likely aridification, but these direct effects of CO2 can also not be ignored. When you get a lot of bush encroachment, it affects systems of animals that depend on grassland ecosystems. You see big shifts in bird richness. The wildlife journalist Adam Welz details in an article for the Guardian how bush encroachment in Namibia adversely affects plains animals like cheetah who need space to hunt, but blind themselves when they run into thorn trees. Vultures may also be affected. After feeding on a carcass they’re very heavy and need a “runway” — space for them to take off again. These are just two interesting biodiversity quirks affected by bush encroachment.
Q: The IPCC “Global Warming of 1.5ºC” Special Report of 2018, the study of 6,000 peer-reviewed papers that has stepped up the global conversation by an order of magnitude, says the world is likely to heat up by a further 0.5ºC — on top of the roughly 1ºC that has occurred since the pre-industrial era — in as little as a decade. Our Burning Planet’s Kevin Bloom reports that, “We have a high likelihood of initiating an irreversible melt of the Greenland icecap and triggering the instability of the Antarctic ice-shelf” between a heating of 1.5ºC and 2ºC. The IPCC Special Report tells us the planet is heating up at 0.2ºC per decade and that South Africa is heating up at “twice the global average”. What does South Africa look like under a global 3ºC rise in coming decades?
A: A 3ºC increase globally would mean a 5ºC or 6ºC increase across South Africa’s land surface and it’s very difficult to imagine that this would not have a very significant impact on South Africa’s fauna and flora, because you fundamentally transform a lot of the interior of South Africa into a bioclimate that looks more like Botswana or southern Namibia. We also know from work done on bird species that such an increase would exceed their ability to regulate their body temperature or that, for example, mammal species at critical life stages like lactation would also run into significant physiological limits. We would see real shifts in the animal richness in areas like Bushmanland. There’s a reason that fauna and flora look the way they do in different bioclimatic zones.
Q: You’ve worked at the coalface of climate fact for decades. How do you cope with the daily barrage of what our world may become?
A: When I lecture, I sometimes ask my students, “Why should I be the only one lying awake at night worrying about this stuff?” And particularly now, with fires raging in the Amazon and the political consequences of seeing the election of ecological vandals like Jair Bolsonaro as president of Brazil, we’re also seeing this destruction in opening up and industrialising the Amazon. It’s very dispiriting because the results are devastating to our ability to keep our emissions below the level that we need to avoid warming the world by more than 1.5ºC or even 2ºC. I’m also deeply concerned about the simplification of biodiversity on our planet unless we get our act together. We’re at risk of losing all the interesting rare species, some of which evolved over a few million years on an Ice-Age planet that was generally cooler than the Holocene era in which we find ourselves.
Q: And yet new research by the University of York highlights that changing climate patterns may even be letting in new species and fuelling diversity. How do these findings stack up against concerns about simplification?
A: How do you fuel more diversity in the remarkable fynbos or in our ancient rich grassland systems? I don’t buy this at all for our systems. Fynbos is a great example of a biome that has evolved all sorts of very interesting biodiversity. You know, long-tongue flies pollinating one particular species — and those are the kinds of things that are at particular risk from the climate crisis. We don’t really know how these ecosystems might behave if they become simplified.
We’re already losing significant chunks of incredibly important and rich species on tropical reefs. This was something we projected way back in the 2007 IPCC report — were some of our projections even too optimistic? We’re certainly seeing some systems degrading at an incredible rate. What that means for places like the Amazon or the coast of Australia…the Great Barrier Reef; we don’t know. We’ll see. We’re also simplifying ecosystems by moving species around, and the invasive species problem is compounding the climate change issue. Are these ecosystems going to continue giving us the kind of services we need? Fresh water? Food? Soil creation and retention? Or is the simplification of ecosystems going to adversely affect their ability to provide those services? Are they going to be as resilient as the more complex systems we have now? We’re running a very dangerous experiment on our planetary system and we’re the guinea pigs.
Q: But your Skype status is “mildly optimistic”?
A: I have been optimistic that the world is really waking up to this issue and responding to it. The youth movements are cause for great optimism. But I’m also depressed by the renewed emergence of ecological vandalism in the policies of those like the Trump administration, Bolsonaro and others. A lot of this is up to our politicians, and all of the people who elect them — do we continue with the experiment, or do we say we’ve learned enough to move onto a sustainable future fast?
I think we’ve learned more than enough. We could have taken significant action in the nineties. But the political shifts in the US, the George W Bush administration, the loss of Al Gore linked to the political shenanigans around the end of that election, the role of the US Supreme Court — these developments have all conspired against us to trip up political momentum at critical times. You watch that tragedy, see a recovery from it, and then Trump gets elected when we could have been making continued progress. It’s deeply, deeply frustrating and I’m angry about it. But what can you do? People have made these political decisions.
I ultimately have some faith that there’ll be enough political will under the UN Framework Convention on Climate Change to allow us to avoid the worst. Fundamentally, I also place reliance in the tremendous resilience of ecosystems as well as in the hope that we have species that are tough enough to continue providing us with the services we need even in a worst-case scenario. The planet has survived being hit by a meteorite several times and life has always recovered — although over tens of thousands to millions of years. DM
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