PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) is one of the most important sources of data for large-scale modelling of how changes in land use is impacting biodiversity. Marry that with future climate models and you have a powerful tool for understanding how these two major factors in global change will shape both biodiversity and human society over the coming decades.
In recent years it’s been a privilege to be part of a project led by Joe Millard and Tim Newbold that’s using PREDICTS to model how pollinators and pollination services are likely to be impacted by human activities. The first paper from that work (which was Joe’s PhD) was entitled ‘Global effects of land-use intensity on local pollinator biodiversity’ and came out in 2021, as I documented on my blog at the time.
Yesterday a second paper was published, this time focused on how land use and anthropogenic climate change interact to potentially affect insect-pollinated crops across the world.
Our main finding is that it’s tropical crops, especially cocoa, mango, watermelon, and coffee, that in the future will suffer the greatest negative impacts from loss of pollinators. Although we can have perfectly healthy diets without consuming any of those, they currently support tens of millions of farmers across the tropics and are part of global supply chains worth billions of dollars per year.
Here’s the full reference with a link to the paper, which is open access:
Insect pollinator biodiversity is changing rapidly, with potential consequences for the provision of crop pollination. However, the role of land use–climate interactions in pollinator biodiversity changes, as well as consequent economic effects via changes in crop pollination, remains poorly understood. We present a global assessment of the interactive effects of climate change and land use on pollinator abundance and richness and predictions of the risk to crop pollination from the inferred changes. Using a dataset containing 2673 sites and 3080 insect pollinator species, we show that the interactive combination of agriculture and climate change is associated with large reductions in insect pollinators. As a result, it is expected that the tropics will experience the greatest risk to crop production from pollinator losses. Localized risk is highest and predicted to increase most rapidly, in regions of sub-Saharan Africa, northern South America, and Southeast Asia. Via pollinator loss alone, climate change and agricultural land use could be a risk to human well-being.
Most of us have at some time stared in fascination at the life contained within the pools that form on rocky shores at low tide. But none of us realized that a whole new class of ecological interaction was taking place!
The 12,000 or so described (and many un-named) seaweeds are incredibly important organisms. Their diverse and abundant photosynthesizing fronds make them one of the main primary producers in coastal seas, creating food and habitat for a huge range of animals. Not only that, but some – the coralline seaweeds – lock up vast amount of CO2 as calcium carbonate and help to create reef systems in the same way as coral.
Although scientists have studied seaweeds for hundreds of years, many aspects of their ecology are still unknown. Their detailed mode of reproduction, for example has only been studied in a small proportion of species.
In a newly published study in the journal Science, French PhD researcher Emma Lavaut and her colleagues have shown that small isopod crustaceans – relatives of woodlice and sea slaters – facilitate the movement of the equivalent of seaweed sperm (termed “spermatia”) from male to female reproductive structures in just the same way that bees and other pollinators move pollen between flowers, so fertilizing female gametes.
Your read that correctly: some seaweeds have pollinators!
It’s an incredible finding! And the implications of this are enormous: Emma and her colleagues have added a whole new branch of life to the examples of sedentary (fixed-place) organisms that require a third party to enable their reproduction. In addition to being a fascinating biological discovery, it has significant environmental and sustainability implications.
Seaweeds are a diverse group of macroalgae that appeared more than one billion years ago, at least 500 million years before the evolution of what we think of as “true” plants, such as the flowering plants, conifers, cycads, ferns and mosses. Sexual reproduction in the brown and green seaweeds, which include kelps, wracks and sea lettuces, involves spermatia that are mobile and use a flagellum to swim through the water to seek out female reproductive structures. However, Emma studied a seaweed, Gracilaria gracilis, which belongs to the Rhodophyta or red seaweeds, and none of the species in this group have these swimming sperm equivalents.
Sexual reproduction in the red seaweeds has therefore always been something of a mystery. Three quarters of species have separate male and female individuals and so they cannot mate with themselves. It was assumed that the gametes were just released into water currents that haphazardly transported them to the female reproductive organs, much as wind pollinated grasses and pine trees release their vast clouds of pollen on land. The authors of this new study, however, point out that most sexual reproduction by these red seaweeds takes place in the relatively still waters of rock pools, a habitat that they mimicked in the laboratory in a series of elegant aquarium experiments.
The isopod crustaceans are attracted to the seaweed because they provide a habitat away from predators and a supply of food: they graze on the microalgae that colonise the seaweed’s fronds. Picking up spermatia and moving them between fronds is a side-effect of this activity by the small invertebrates. As you can see from the illustration above, the isopods and the seaweed are engaged in a “double mutualism“: a plus sign (+) indicates a positive effect of one species on another, while a minus sign (-) indicates a negative impact.
What I find especially fascinating about this research is that both the seaweed (Gracilaria gracilis) and the isopod (Idotea balthica) were originally described as species more than 200 years ago. They also have an extremely wide distribution. The isopod is found around the coasts of Europe and down the eastern seaboard of the Americas. The seaweed is pretty much found globally. These are not rare, unusual species, yet the interaction between them has only just been discovered! This is a point that I made in my recent book Pollinators & Pollination: Nature and Society: quite often, species that are well known interact in previously undocumented ways because no one has had the time or inspiration to look closely at them.
Although the idea that small sea creatures might be helping seaweeds to reproduce sounds very fanciful, there is a precedence for this discovery. Back in 2016, in a paper published in Nature Communications, a group of Mexican researchers led by Brigitta van Tussenbroek showed that a species of seagrass is pollinated by a diverse assemblage of small crustaceans and polychaete worms. Seagrasses are flowering plants, not seaweeds, but clearly this type of mutually beneficial relationship can exist between different species in the oceans.
Rhodophyta are the most diverse group of seaweeds, with more than 7,000 known species. They are especially abundant on coastal shores, oceanic habitats that are under huge pressure from infrastructure development, pollution, and climate change. At the same time, these seaweeds are economically important and millions of tonnes of them are collected every year as food, as nutritional and pharmaceutical supplements, and to produce agar. In order to conserve these seaweed populations, we need to better understand their ecology and their environmental requirements.
The work by Emma Lavaut and colleagues suggests that interactions with their “pollinators” may be a critical aspect of this understanding. In the same way that “Save the Bees” has been a rallying call for conserving interactions between species on land, we may soon hear this message echoed in “Save the Isopods”. At the very least, I have to add a new section to the second edition of my book!
Full disclosure: I was one of the reviewers of the original manuscript submitted to Science by Emma and her co-authors. It’s a rare privilege to review a study and think: “Wow! This is a game-changer!” and including this paper it’s happened to me only a handful of times. The editors at Science kindly invited my colleague Dr Zong-Xin Ren and myself to write a Perspective piece about the work and we were delighted to do so.
Image credits: Isopod and diatom images from Lavaut et al (2022). Gracilaria image by Emoody26 at English Wikipedia CC BY 3.0 https://commons.wikimedia.org/w/index.php?curid=3455016. Design by Shijia Wen and Jeff Ollerton.
An interesting study published this week in the journal Science has provided more evidence that natural regrowth of forests is faster and more efficient than tree planting for restoring habitats. Here’s the Guardian‘s take on it:
Tree planting has its place, of course, especially as a way to get local communities engaged in positive action for the environment. But it’s not the solution for large-scale habitat restoration: in order to do that we need to harness nature’s own regenerative abilities.
My summer reading this year has included two books that I’ve really looked forward to, and which have not disappointed. These books are on the one hand very different and yet share enough similarities for me to review them together. Michael E. Mann’s The New Climate War focuses on the ‘climate emergency’ whilst Dave Goulson’s Silent Earth is about the ‘ecological emergency’, and specifically the decline of insect populations. As I pointed out in arecent New Scientist opinion piece: “the climate emergency often overshadows the ecological emergency, even though the two overlap both in their causes and their solutions”. Reading these two volumes in parallel has given me a much deeper understanding of just how true that statement is, and it’s why I’m suggesting that of the many, many books that have been recently written about our current environmental crisis, these deserve to be the ones that you read.
Silent Earth deals with the billions of small things – the insects and other invertebrates – that make the world function the way it does. These creatures facilitate the recycling of organic material, the pollination of wild and crop plants, the regulation of populations of other species, and play a host of additional ecological roles. The central thesis of the book is that the growing evidence of declines and extinctions of these small animals should give us cause for concern. In contrast, The New Climate War is about the big stuff – how the world’s atmosphere and oceans are heating up, the contribution of human activities to that warming, and what this means for weather patterns and sea levels across the globe. And how industry and politicians have conspired to deny, obfuscate, and divide, undermining efforts to decarbonise the world’s economy.
It matters not whether we view the world through a microscope or via an Earth observation satellite, both of these ways of seeing and understanding are important to our future as a species. The flap of a butterfly’s wings may only rarely be the indirect cause of a hurricane in the Caribbean, but reading these books nonetheless reminds us of the connections between the world’s biosphere and its physical domains.
The science underlying both books acts as a background to their main purpose: convincing the reader that there are urgent issues with which we, as a society, must deal. In this respect they are unapologetically political, and the point at which science meets environmentalism. The books are written by scientists who are respected experts in their respective fields, but who are not content with sitting back on their award- and citation-laden laurels, and allowing their science to speak for itself (as important as that is). Both Mann and Goulson have entered the more public arenas of politics and social commentary to argue the case for fundamental restructuring of some aspects of our societies. Their reward has been near constant criticism, much of it personal, vindictive and even threatening, by the vested interests of the fossil fuel industry (Mann) and agro-chemical & farming interests (Goulson) and the keyboard warriors who labour on their behalf, wittingly or not. That Mann and Goulson persist in voicing their concerns in this way, at the same time continuing to publish high quality science, says much about them as people and their commitment to these important causes.
The stereotype of the cold, calculating, emotionless scientist is shattered by these authors as they frequently refer to their families, especially their children, as a prime motivation for their activism. In an emotive chapter, Goulson imagines his son as an old man sitting up through the night to defend the vegetables that he’s growing with his family in a Britain that has experienced not an apocalyptic collapse of society and basic infrastructure, but “a slow unravelling over decades”. As he remembers back to the world of his youth he wonders: “Why did we fail to act? We humans do not seem to be very good at grasping the big picture”.
The Big Picture is certainly an underlying theme of both books, despite the different scales at which these scientists work, and both are revelatory in their descriptions of what’s occurring behind the scenes. Pull aside the curtain and we see the financial connections between various anti-environmental think tanks and lobby groups (Mann) and the hypocrisy of large business corporations which continue to manufacture highly toxic pesticides that, although banned in the west, can be profitably exported to developing countries (Goulson). All of these messages of corruption and environmental degradation could make the books pessimistic reads. But in fact both have an optimistic undertone, a sense that we know what the issues are, we know what’s got us into this mess, and there are routes out of it. But only if (and it is a huge if) there is the willingness of governments and large corporations to act.
Both writers share a belief in humour and personal anecdotes as vehicles for emphasising important points. For example Mann describing the fearsome and brutal attention given by climate deniers to Greta Thunberg and other youthful activists as being like the Eye of Sauron (one of several Lord of the Rings analogies). Or Goulson’s description of giving a phone interview to Australian radio while lurking in the piss-smelling toilet of a British pub. These books are brought to life by the authors’ experiences as scientists and as advocates, and their passionate wish for a better future.
Full disclosure: this can hardly be considered an objective review as both Dave Goulson and Mike Mann are friends of mine. Dave I met over thirty years ago when we were graduate students in the same department, and we’ve published a few things together. Mike I encountered much more recently, as I described in this post, when we were concurrently on sabbatical at the University of New South Wales and discovered that we were living in adjacent apartment blocks. In some respects the world of science is a very small one. Despite these personal connections I don’t think that I would have said much that’s different about either book had I not known their writers. But who knows, that’s not the way things are. There are certainly things to criticise in both books, and I don’t agree with all of the writers’ conclusions and could debate several points of interpretation with them, especially in Silent Earth where I’m in more comfortable territory. But those would be minor criticisms in light of the conclusions that these important books draw: that our world is changing rapidly, that we are responsible, and that we have a duty to act immediately. It’s not too late, but we need to listen to the science and what scientists such as Mann and Goulson are telling us.
Watch out for my article in Bees and Other Pollinators Quarterly Magazine about what the forthcoming COP26 climate change meeting has in store for pollinators, including why commitments to developing countries are important and the Grasslands+ initiative.
The magazine is in the shops on October 12th or you can subscribe by following this link: https://bq-mag.store/
Over the past few months I’ve been thinking a lot about the relationship between the “Climate Emergency” (CE) and the “Ecological Emergency” (EE), and how they overlap considerably in terms of causes and solutions, but that the priorities of the CE often trump those of the EE. One of the outcomes of this has been a commentary that’s been published in New Scientist this week. It’s free to access – here’s the link:
It’s extracted from a much longer article that discusses the role of pollinators in relation to climate change. Hopefully that will be published in the not too distant future.
The other thing that’s happened this week is that, in my role as Visiting Professor of Biodiversity at the University of Northampton, I was asked to take part in a webinar that’s one of a series being produced in support of the Levelling Up Goals. The LUGs, modelled on the UN’s Sustainable Development Goals (SDGs) have cross-party support in Parliament and aim to bring economic prosperity to those parts of the country that have lagged behind in recent decades. The “Green Economy” is seen as central to this.
It was interesting and I learned quite a bit, for example about how the government is investing the state pension pot in sustainable energy projects. The format of the webinar, however, with the chair asking individuals a question and each of us responding, was a little frustrating as there was no real opportunity to counter statements being made, particularly by the MP for Hexham.
Yesterday Karin and I had out first COVID-19 vaccination; today we both feel a little under the weather, but it will pass. It’s certainly better than the alternative!
The nice people at NHBS recently did a wide-ranging interview with me about my new book Pollinators & Pollination: Nature and Society and what led me to write it. It covers a lot of ground, including climate change, food security, the UK Pollinator Monitoring Scheme, and growing up in Sunderland.
There’s been much discussion in the news and online recently about seed collecting, habitat restoration, and tree planting as a way of storing carbon in an effort to reduce the effects of climate change. This is one of the (many) elements proposed by the recent Drawdown Framework. In fact their “Table of Solutions” ranks tropical forest restoration in the top 5 to 10 ways of reducing CO2 in the atmosphere, and temperate forest restoration and planting in the top 20.
Grain for Green – China’s attempt to restore vegetation to abandoned farmland to reduce soil erosion and flooding. According to the Wikipedia entry “Grain for Green has involved 124 million people in 1,897 counties in 25 provinces……. By 2010, around 15 million hectares of farmland and 17 million hectares of barren mountainous wasteland were converted back to natural vegetation”.
Great Green Wall – a multinational initiative in Africa aimed at restoring the vegetation on the southern edge of the Sahara to combat desertification and mitigate climate change.
Several countries have also made a great deal of noise about marshaling huge public efforts to plant hundreds of millions of trees in a single day, for example Indiaand Ethiopia.
These big schemes are all well and good: they generate a lot of publicity for actions on climate change and a warm, fuzzy feeling that governments and people are Doing Something. But there’s a couple of problems. First of all, planting trees is not enough: we could not plant enough trees in the world to reduce CO2 to pre-industrial levels. Secondly, planted trees require nurturing. It is not enough just to put in some young plants and hope for the best; a high proportion of trees die even when well looked after. If they are just planted and ignored, who knows how many will survive?
However habitat restoration is important; it’s not a silver bullet solution to climate change, but it is part of our toolbox of Things We Can Do. Just as importantly, restoring habitats provides more opportunities for species to move in response to changing climates, and to recolonise areas from where they have been extirpated. And of course diverse, functioning ecosystems support human societies in ways both tangible and unquantifiable.
With all of this in mind I was interested to read a piece by John Carey in PNAS entitled “The best strategy for using trees to improve climate and ecosystems? Go natural“. There’s some really inspiring stories in here, it’s well worth taking a look. The main message of the article is that allowing forest vegetation to naturally regenerate, from seeds, and dormant roots and stumps, is by far the best way to ensure that trees survive and the restoration is successful. However there’s something fundamental missing from that article: the role of species interactions in determining the survival of these forests over long time scales.
The vast majority of the world’s plants are animal pollinated; this includes trees. Even in the UK where we often associate trees with wind pollination, about 65% of our native species are insect pollinated. In the tropics this can rise to 100% of species within a community. Although many of those trees can engage in some self-pollination, in the long term this is likely to result in genetic problems associated with inbreeding. Outcrossing sex is common in plants for a good reason.
Similarly many trees require animals to move their offspring away from the parent plant. This avoids competition between parent and offspring, and the impacts of diseases and pathogens caused by the Janzen-Connell Effect. I don’t have any comparable statistics on the proportion of trees, regionally and globally, that use animals as seed dispersers (does anyone? Please comment below if I’ve missed something). But I’m willing to bet that it’s a high proportion.
Without pollinators and seed dispersers, restored forests will not flourish in the long term. There seems to be an implicit assumption that once the forests are established, the pollinators and seed dispersers will follow. That may be true up to a point, but it shouldn’t be taken for granted, particularly for isolated fragments of forest with no ecological connections to more established areas of woodland. These are the aspects that are missing from John Carey’s (otherwise fine) article, and indeed from wider discussions about forest restoration and tree planting. As so often when we talk about the conservation of biodiversity we neglect to consider the role of species interactions. I’ve been trying to press home that point for years, on the blog and in papers, and I was pleased to see an interesting contribution to this topic by Pedro Luna and colleagues from Mexico on “Measuring and Linking the Missing Part of Biodiversity and Ecosystem Function: The Diversity of Biotic Interactions“.
Let’s not forget: species do not occur in isolation, and the biodiversity of species interactions in fundamental to the ecology of the planet.
In my last post I highlighted a couple of recent papers on climate change and extreme events, and how they impact pollinators. The Erenler et al. (2020) mini-review paper that I mentioned has now been published and is available for free download for the next 50 days. Follow the hot link here:
This review is one of several from a themed issue of Current Opinion in Insect Science devoted to Ecology. The issue is edited by Tom Ings from Anglia Ruskin University and Sarah Arnold from University of Greenwich.
Well, we’re back in the UK now and have just about got over the jet lag. I’ve returned to teaching, admin, and meetings, and both Karin and I are trying to find time to finish our books. But the persistent backdrop to our stay in Australia – the bushfires and the role of climate change, and the ensuing tensions between scientific evidence and politics – is still fresh in our minds. It’s timely, then, to highlight two new papers that focus on extreme events, climate change and pollinators. The first is one of my own, led by Dr Hilary Erenler who carried out her PhD research in my group. It’s an invited mini-review in the journal Current Opinion in Insect Science entitled “Impact of extreme events on pollinator assemblages” (Erenler et al. 2020). The review is available as a pre-print on the journal’s website; we’ve not yet even seen the proofs, though the final version should not be too different. If you want a copy, just ask.
In this essay we focus on what we term SHOCKS: events that provide a Sudden, High-magnitude Opportunity for a Catastrophic ‘Kick’ to the environment that can negatively affect pollinator assemblages in many different ways. Such events can be natural, human-mediated or human-enhanced, and occur suddenly, at a high-magnitude and with possibly catastrophic outcomes for those pollinators. There are many examples of such SHOCKs, as we illustrate in the figure above which comes from the paper. However one of our main conclusions is just how little we understand about the outcomes of such events on pollinators. Ideally we need before, during and after event monitoring to assess how pollinators have been affected and may respond. But SHOCKs are, by their very nature, infrequent and unpredictable, and often we don’t have the baseline data with which to compare to post-event data. I know from conversations with Australian pollination ecologists that some have had their field sites burned and they are going to use this as an opportunity to assess how the fires have impacted pollinators. Field experiments such as the one by Biella et al. (2019) that I discussed last year, in which flowers were removed from a plant community, may also give us some insights into the response of plant-pollinator networks to sudden SHOCKs. But we need more research focus on this topic, especially consideration of how the impacts of SHOCKs can be reduced and mitigated.
One set of emerging human-enhanced SHOCKs highlighted by Erenler et al. (2020) is extreme weather events that are being exacerbated (in scale or frequency) by anthropogenic climate change. We cite several papers and reviews that have considered this, but there’s still few empirical studies that have actually looked at how weather SHOCKs might be impacting pollinators. It’s therefore timely that this week’s Science includes a very impressive study of how climate change has affected populations of bumblebees (Bombus spp.) in Europe and North America (Soroye et al. 2020).
The title of the paper rather gives away its findings: “Climate change contributes to widespread declines among bumble bees across continents“. This study shows that, for the 66 species of Bombus studied, there had been a decline in species diversity in 100 km x 100 km quadrats of, on average, 46% in North America and 17% in Europe. This loss of diversity has occurred in the period 2000–2014, relative to a baseline of 1901–1974. Using some sophisticated analyses they show that climate change has been the main driver of these losses, and has been more important than factors such as changes in land use, pesticides, etc. Which is not to discount those other contributors to pollinator loss: they can interact with climate change and are all part of the assault that we are imposing on the environment.
The most significant finding of the Soroye et al. (2020) study, and the reason why I’m discussing Erenler et al. (2020) in the same post, is that it’s extreme heat which seems to be the driving factor in determining Bombus declines. Bumblebees are large, hairy insects because they are adapted to cooler conditions: they are not, by and large, tropical insects, except in mountainous areas. Not surprisingly, then, it is the number of days of temperatures higher than those historically encountered by particular bee species that is the main driver of their loss from a region. In relation to the figure above, this is the result of human-enhanced SHOCKs, and for heat-sensitive species like bumblebees, they are occurring more often than we had imagined when we wrote our review. I fear that the coming years will see more examples of this as the effects of anthropogenic climate change continue to play out and our world experiences more extremes of weather events that are hotter, wetter, colder, drier, windier, and more combustible than we have previously known.
References
Biella P., Akter A., Ollerton J., Tarrant S., Janeček Š., Jersáková J. & Klecka J. (2019) Experimental loss of generalist plants reveals alterations in plant-pollinator interactions and a constrained flexibility of foraging. Scientific Reports 9: 1-13
Erenler, H.E., Gillman, M.P. & Ollerton, J. (2020) Impact of extreme events on pollinator assemblages. Current Opinion in Insect Science (in press)
Soroye, P., Newbold, T. & Kerr, J. (2020) Climate change contributes to widespread declines among bumble bees across continents. Science 367: 685-688 [see also the commentary by Bridle and van Rensburg pp. 626-627 of the same issue]
Prof. Jeff Ollerton - ecological scientist and author 