How representative of ecology are the top 100 papers?

The publication in Nature Ecology & Evolution of the 100 most important papers in ecology has led, inevitably, to a fierce debate. Several rapid responses are already in review. The main bone of contention has been that not only were the first authors of 98% of the papers male, but the only two papers written by women were relegated to the very bottom of the list. In a generous reading this reflects implicit biases at every stage of their compilation, rather than any malign intent on the part of the authors*, but I’m sure they’ve received plenty of feedback on this oversight.

Pretty soon after it came out, Terry McGlynn on Twitter asked:

If you want a guide to all the essential papers that didn’t make the list, and happen to have been written by women, this thread is a good place to start. I’m not going to fan the flames any further here, but it’s important that this glaring omission remains the headline response. Instead I’m going to respond to another observation:

This pricked up my senses, given that I am also an undergraduate textbook author. In writing the Natural Systems book (published 2016) I made a deliberate attempt to not cite the same things as everyone else, and to emphasise promising directions for the future of the field of ecology. That made me wonder: how many of the 100 most important papers in ecology did I manage to cite? Note that I had no input into the Nature Ecology & Evolution article, and the book only includes references up to the end of 2014, so these form entirely independent samples. Without formally counting, I estimate that I’ve read around 80% of the top 100 papers, and I’m aware of almost all of them.

How many? Only 17/100 papers.** That raw figure disguises some interesting discontinuities within the list. Of the top ten I actually cited six, and a total of nine from the top twenty. This indicates a reasonable amount of agreement on the most important sources. But of the bottom 80 I only managed another eight (10%). This comes from a total of over 800 sources cited in the book.

Why did I cite them? The main reasons:

  • Posing an important question we have since spent a long time trying to answer (Hutchinson 1957, 1959, 1966, Janzen 1967).
  • Defining a new idea which remains relevant (Grinnell 1917, Gleason 1926, Janzen 1970, Connell 1978).
  • Creating a framework which has been elaborated since (MacArthur 1955, MacArthur & Wilson 1963, Tilman 1994, May 1972, Chesson 2000, Leibold et al. 2004, Brown 2004).
  • Reviewing the evidence for an important principle (Tilman 1996).
  • The first empirical demonstration of an important idea (Tilman 1977).

In many cases I have cited the same authors from the top 100 multiple times, but not necessarily for the original or classic piece of work; often it’s a later review or synthesis. This is because I deliberately chose citations that would be most helpful for students or other readers, not always on the basis of precedence.

The aim of this post is not to argue in any way that the authors of the paper were wrong; this is only a reflection of my personal opinion of what matters in the field. Theirs was generated through the insights of 147 journal editors and a panel of 368 scientists from across the discipline, and is therefore a much more genuine representation of what opinion-makers within the field of ecology believe (although there are better ways to conduct such an exercise). Mine is only one voice and certainly not the authoritative one.***

Writing a textbook is something like curating an exhibition at a museum or art gallery. It bestows on the author the responsibility of deciding which pieces to show in order to tell a particular story. Of necessity this becomes a very personal perspective. I’m amused to find that my view of ecology overlaps by only 17% with the leaders in my field.**** That doesn’t make either of us right or wrong, only that we must be looking in very different directions.

As for their aim of creating an essential reading list for post-graduates or those wishing to learn the foundations of the field, here I profoundly disagree. The best way to learn about current practice in ecology is to start with a good core textbook (and there are lots more out there), read recent synthetic reviews, or pick over the introductions of papers in the major journals. In the same way that you don’t need to read Darwin to understand evolutionary theory, or Wallace to understand biogeography, it’s not strictly necessary to read Grinnell, Clements or Gause to get to grips with modern ecology. Fun if you have the time but most people have more important things to do.

One final comment: three of the top ten papers in ecology were written by one man, G. E. Hutchinson. There is no doubt that his work was highly influential, and I agree that these are important papers to read. What I find most interesting though is that all of them are essentially opinion pieces that frame a general research question, but go little further than that. None of them would get published in a modern ecological journal.

Where would you find similar pieces of writing today? On a blog.


UPDATE: Dr Kelly Sierra is soliciting suggestions for a more inclusive list. Whether or not you feel that such lists have any inherent value, if we’re going to make them then they should at least represent the full diversity of our scientific community.

* In the comments below, Jeremy Fox points out that this isn’t very well worded, and could be read as a suggestion that I think there was some malign intent. So, to be absolutely clear, I am not suggesting that the authors made a deliberate choice to exclude or devalue papers written by women. If anything this was a sin of omission, not of commission, and we all need to learn from it rather than attribute blame to individuals.

** As an aside, 16 of the 17 were sole-authored papers. Only Leibold et al. (2004), which defined the metacommunity concept, had more than one author.

*** Nor do I think it’s healthy for there to be a voice of authority in ecology, or any other academic field. We make progress through testing every argument or piece of evidence, not by accepting anyone’s word, however senior or trustworthy. If there were an authority figure you can almost guarantee that I would disagree with them.

**** I’m more in line with the recent attempt to define the 100 most important concepts in ecology, although a little peeved that so many people dismissed Allee effects given my recent work on them.

Are conkers getting smaller?



A selection from this year’s unimpressive crop of conkers.

It’s a sign of age to notice that many things appear smaller than they used to be: chocolate bars, coins… and conkers.

Hold on. Conkers? Surely the same trees, growing in the same places, can’t have suddenly started producing smaller fruit? Well it seems that they have, and I’m not the first to notice, although hard data on sizes over time has proven elusive. Even so, it’s pretty obvious to me that this year’s crop provides relatively few conkers that would be worth putting on a string. One wonders how the Conker World Championships (and yes, they do exist) are going to respond to this threat*.

Conkers come from the horse chestnut tree, Aesculus hippocastanum (I have a video about it). It’s not native to the British Isles, coming instead from the Balkans, although like many immigrants it has embedded itself in the culture of these islands such that it would be strange to imagine it not being here. There are something like half a million horse chestnut trees in the UK, but they aren’t often found in our woodlands. The overwhelming majority are planted in parks and urban streets, and therefore we encounter them frequently in our daily lives. They also naturally spread into disturbed habitats around towns such as railway sidings or abandoned land.

In the last few years horse chestnuts have started to suffer from two problems. One is the horse chestnut leaf miner, a species of moth that was first discovered in 1985 in northern Greece, and only described as a new species the following year. It then spread rapidly throughout Europe, reaching the UK in 2002, and since then has reached all parts of the country. This is the main reason why the foliage of horse chestnuts starts to turn brown in August (or sometimes even earlier), long before it would naturally begin to yellow at the onset of autumn. The caterpillars actually live inside the leaves, eating away at the green tissue while protected by the tough upper and lower layers.

The leaf miners aren’t a risk to the tree’s survival — afflicted trees still generate a fresh flush of leaves the following year. What the leaf damage does, however, is to restrict the resources available to trees just when they’re getting round to producing the year’s crop of conkers. For a tree, the year is like a marathon; they spend many months storing up energy, biding their time, and around the end of August launch into their sprint finish, culminating in the release of thousands of fruit. The arrival of the leaf miner is like hobbling them halfway through the race. They can still make it to the line, but they don’t have enough energy left for the grand finale.


Evidence of the leaf tunnels created by the horse chestnut leaf miner. This tree is right outside my building, and every tree on campus looks much the same.

If your trees have leaf miners, then there are some things you can do, such as removing the leaves that fall and composting them, burying them (at least 15 cm / 6 inches deep) or, if it’s the only option, burning them. This will kill the pupae of the moth which are overwintering, but it won’t prevent reinfection from other trees in the neighbourhood, which is highly likely to occur. Some birds such as blue tits have learnt to recognise and eat the leaf miners, but this is unlikely to control them effectively because the main damage is done later in the summer once the fledgelings have already left the nest, so there is less feeding pressure.

This isn’t the only issue affecting horse chestnuts though. A new disease known as horse chestnut bleeding canker was discovered around ten years ago, and is now also widespread. It may have infected around half of British horse chestnuts. This causes scars on the stem which ooze sap. Not all trees are killed by the disease; some survive, while others might be immune. Nevertheless, many trees are weakened by it, and a number have already died. This hidden problem might also be part of the reason why our trees are struggling to produce conkers of the same quality as before.

There is some debate over whether the two problems, the leaf miner and the bleeding canker, are related to one another. Some early experiments suggested that seedlings with leaf miners were more vulnerable to the effects of the disease, but more recent and large-scale surveys have found no association between the two. The balance of evidence at the moment therefore indicates that they are independent problems. There is at present no cure for the disease, although some very recent work published earlier this year implies a role for the bark microbiome in regulating the severity of the disease.

A citizen science project has been tracking these new arrivals throughout the UK, and in 2013 found that parasites of the leaf miner have been catching up. This is good news, as it might mean that natural biological control could eventually restrict the impact of the miners.  They are still asking for data and there are lots of nice resources on the website which could be used in classrooom teaching to engage schoolkids in observing an interesting phenomenon**. Children might not be able to play conkers in quite the same way, but why not use this as an excuse to teach some exciting ecology!

* Interestingly, the game of conkers predates the arrival of the horse chestnut tree in the UK, and was formerly played with snail shells or other objects. This would imply a rather radical shift in the modern rules though.

** You should also look at the OPAL national tree health survey, which involves recording observations on a whole range of trees as well as horse chestnut.

What’s the worst that could happen?

Picture 099

I’d be happy to never have to fly in one of these ever again.

I never intended for the expedition to end with me pulling one of my students out of a river after a packhorse fell on top of her while crossing. We were in Kamchatka, Far East Russia, one of the remotest corners of the world, surveying forests. This was to be our last day in the field. We had just broken camp and begun the day-long hike back to the village where we would collect our samples, have a farewell party and make our way back to the UK. Instead we ended up requiring a helicopter evacuation and spent much of our remaining time dealing with Russian hospitals and insurance claims.*

On the other hand, we had planned for this. Well, not for this precise eventuality, but we knew what to do when it happened. Actually our Plan A failed, but we were sufficiently well-prepared that Plan B came through. This played a major role in ensuring that the student in question returned home safely and made a full recovery.**

At this time of year the thoughts of many ecologists turn to where they will be next summer as they begin putting together grant applications. This is therefore the right time to start planning not only for the fun parts — where you’re going, what data you’ll be collecting, who will be coming with you — but also asking what’s the worst that could happen, and being fully prepared. It’s your responsibility to keep your team safe, even if sometimes they don’t like being told.

I sit on the grants committee of the British Ecological Society. If you’re applying to us for funding in the current round, you’ll notice that there’s a box for you to comment on safety planning. This is not merely a procedural step. I’ve been known to shoot down proposals where there has clearly been inadequate consideration of the hazards involved in a project. You don’t need to have direct personal experience of the site or procedures (although that helps), but you need to convince us that you’ve taken good advice and planned accordingly. Why should funding bodies care about your risk assessment? Apart from a genuine concern that fieldwork is conducted with high safety standards, there is also a potential reputational risk if a trip that we’ve financed goes badly wrong.

Picture 113

Hey, don’t judge the quality of the plaster cast. It did the trick for as long as we needed it to.

My experience comes from not just living through a crisis on an expedition, but participating in or leading a large number of trips in which nothing serious happened. There were problems and near misses, and we learnt from them. I’m also on our university panel for assessing remote field trips from many different faculties. We have people working in war zones, refugee camps, polar ice-caps and coral reefs. It’s rare that any location is declared entirely unsafe to work in (but check the latest warnings from the FCO); with good planning we’re happy to send people almost anywhere. So here are some general guidelines.

1. Know the rules: the Royal Geographical Society no longer publish their excellent Expedition Handbook in hard copy, but the good news is that the chapters are freely available online. This includes six chapters on Health and Safety; there’s much more good advice elsewhere on the website. If you’re in the UK then the regulatory standard for activities outside the UK is BS 8848. This is the legal standard by which you can expect to be judged if anything goes wrong, so make yourself familiar with this.

2.  Training: having someone with medical training is essential. This doesn’t need to be to professional standards; there are specific courses that cater for the types of situation you’re likely to encounter on expeditions, as well as guidance on what you need to know. It’s just as important to know how to deal with the trivial stuff as it is to recognise when you need to call for help or evacuate. This is a standard much higher than a normal workplace safety course. First Aid training is intended to help you keep someone alive until the ambulance arrives, ideally within the hour. If the ambulance isn’t coming you’ll need a higher level of competence. I would ensure that at least two people are trained, not only in case one of them gets injured, but because when you do have to look after a casualty it helps to have several people taking turns.

Also consider leadership training, especially if you haven’t had much expedition experience. I’ve not done any of these courses but a quick online search suggests that there are plenty out there.

Picture 174

Any ambulance is super if it turns up.

3. Insurance: most holiday travel policies will not cover a remote casevac (casualty evacuation). You need to make sure that you have specific cover for the activities you’re doing and the full costs of evacuation and medical care. I’m lucky that our university provides this, though only on condition that we meet stringent standards for our planning.

More to the point, a helicopter won’t even take off without being certain that someone is going to pay them. They don’t fly on goodwill and hope. Just as important as having the insurance is knowing who to call to access it, and making sure that the agencies coming to your rescue know that you’re a paying customer. Find out where the helicopter station is (or the coastguard, or whoever you’re relying on for rescue), and it does no harm to drop in right at the start of the trip and let them have your location and insurance details.

4. Get advice. Within the UK, the Foreign and Commonwealth Office travel guides are a useful first point of reference. Others who have been before you will be a trove of useful insights, including things you perhaps haven’t thought of yet.

Most importantly, always talk to locals. They will have the greatest awareness of specific hazards and how to deal with them. For example, I don’t worry overly much about brown bears in Kamchatka because I know that in the areas where we work, they won’t have encountered many people, and the only ones they will have seen are hunters. This means that they’re relatively timid: they run away if they hear you coming, and they avoid our camps. I would be much more cautious in Yellowstone, where bears are habituated to the presence of humans and associate us with food. Bears are always a risk but how you respond to this depends very much on the local context.

5. Buy the right equipment. We didn’t have satellite phones in Kamchatka because it’s still a militarised zone and they’re banned. We did, however, carry an EPIRB (Emergency Position Indicating Radio Beacon), and while these are more common on ships, there are lightweight ones that fit easily in a rucksack. You’ll need to register it first with your local in-country agency and check on the regulations for wherever you’re going. Another alternative is the SPOT messenger, which are small and easy to carry, but global coverage isn’t quite complete. I would strongly recommend having multiple methods of summoning help, and even with all this modern technology, I still insist that everyone on my teams carries whistles and flares.

6. Complete your risk assessments and ensure everyone has read and agreed to them. Your workplace will have a safety officer, an agreed procedure and a set of standard forms. Moan as much as you want about this — everyone does — but don’t let that get in the way of actually doing it. The process exists to protect you, your colleagues and everyone working with you. Don’t omit any local guides, staff and collaborators: they also have a role to play in overall safety. (As an illustration, our accident was directly caused by the local guide.)

7. Do you have a code of conduct and sexual harrassment policy? If not then you are placing members of your team at risk, so you need one, then demand that everyone has  read and understood it, preferably by forcing them to sign a form.

8. Follow through: risk assessments often make noble claims about how they’re going to keep in touch with people back at base, fill in log-books, text GPS locations on a daily basis, call a named contact at the same time every day… all these promises. Some of them are overkill, and I’ve stopped believing many of them. Safety planning isn’t there just to satisfy your insurers, and it shouldn’t be forgotten the moment you get to the field. Make time to role-play a casevac as part of the on-site induction, then conduct regular self-assessments and checks throughout your trip.

Most of all, remember that safety planning isn’t about removing risks altogether, but knowing how to reduce them and cope when the worst happens. Our story had a happy ending, and has since been used in courses as an example of best practice, but only because the groundwork had been put in place long beforehand. Start now.

* Here’s a newspaper report from the time; it’s not wholly accurate but you get the picture.

** Kim is now completely fine. As evidence, here’s a recent photo of her quite deliberately putting herself in harm’s way:


Honestly Kim. Will you never learn?



The Bill Effect


Entrance stone at Newgrange, Ireland. The upper opening is aligned such that once a year, at the winter solstice, the sun shines directly through and illuminates the interior. Picture by Ceoil and used under Creative Commons Attribution-ShareAlike 3.0 License.

As graduate students at the University of Leeds, there was a well-known phenomenon known as the Bill Effect. It could only be observed in a single location, the office of pollination ecologist Bill Kunin*. I experienced it on several occasions and it reverberates still.

Back then, for us, Bill was an intimidating person to talk to. Not because he was unfriendly; far from it, he’s one of the most genuinely warm and approachable people I’ve met in my career, and he always made time to help those students who needed him. His enthusiasm, encouragement and collegiate spirit have no doubt propelled many young scientists into successful careers**. Don’t get me wrong, Bill is great.

There was one minor barrier to a meeting with Bill, though largely practical and psychological. His office was opposite my lab, and therefore easily accessible, although he wasn’t my supervisor. But to meet him, you had to knock very loudly, then listen carefully for a response. I distinctly remember the view: an old fridge stood by the door, atop which sat a teetering mountain of stained mugs which had been used, set down and forgotten (the occasional Cleaning of the Mugs was a festival in the department calendar; suddenly the kitchen would be restocked with drinking vessels). Many a student with an appointment would knock timorously then hover outside in nervous apprehension. Bill, deep within, probably didn’t even hear them.

Two things set Bill apart. The first was that he spoke maths (or more correctly, being American, ‘math’). On our explaining some half-formed idea or incomplete hypothesis, his first instinct would be to formalise it as an equation. Now for young biologists this was a terrifying proposition. These simple functions appeared as arcane runes because our training in this regard had been so poor. In the UK it’s unusual for an undergraduate biology degree to contain much calculus, or indeed any maths beyond an applied approach to statistics. Likewise our post-graduate degrees lack any training element that would compensate for this. To cut a long story short, UK biology post-grads are in general pretty terrible at maths, and it’s not their fault.*** Talking to Bill meant confronting this insecurity.

The second was that Bill had a knack of asking the question beneath your question. This can be disconcerting to a postgraduate, who is usually interested in the answer to a single, practical issue, whatever is impeding their progress at that precise moment. Bill would seldom give you the straight answer that you desired; more often he would drill down and enquire as to what had brought you to this point. Being forced to describe and justify your underlying rationale can be alarming, especially if you’re not fully prepared for it.

This is when the Bill Effect would manifest itself. He would take the bare bones of your problem, weakly expressed as they were, and construct a logical argument before your eyes. As he declaimed his solution, hands whirling in enthusiasm, it was as though the heavenly spheres had aligned, and the bright light of understanding was shining directly upon you. Suddenly all was clear, suddenly it all made sense! It was exhilarating, and you left his office infected with his passion and positivism.

Sadly the Bill Effect was also fleeting; on leaving the office, within a few steps I had usually lost the thread of his argument, and by the time I sat down, it was entirely gone. Later I learnt to take notes but the first few times his insights simply evaporated before I was able to put them into practise. That simple discipline, however, of reverting to the fundamental basis of what I was trying to achieve, was always a worthwhile end in itself.

Why am I writing about this now, a good 15 years later? Well, I’m trying to think about how to be a more effective PhD supervisor to the post-graduates in my own group and those who consult me for advice. I don’t know what kind of PhD supervisor I am; I leave that for them to decide. Instead I’m thinking about the types of interaction with academics that left the most lasting impression on me over the years. Sometimes these were uncomfortable, intellectually challenging or emotionally draining, but they have stayed with me because they formed an essential part of my training, and have shaped my thinking for years thereafter. I would like to be able to recreate them for my own students; in this case by not just answering the simple question, but taking the time to understand a problem in its entirety and attempting to resolve it from the ground up.

If you’re a PhD student, there may be a member of staff in your department who fits the description above. They might even be your advisor or supervisor, in which case you’re very fortunate. My advice: seek them out. Expose yourself to thoughtful, critical, constructive scrutiny. It won’t be easy, and at first a lot of their insights might not stick, but in the long run it will make you a better scientist. Eventually you’ll realise that they’re having fun thinking about your problem, and that means so can you.


* Bill is still at Leeds — it would be interesting to hear from current post-grads whether he retains this particular power.

** He was so fired up after my talk at BES 2016 that he high-fived me, which I regard as an esteem indicator. I wish I could put it on my CV.

*** For this reason I prefer to take graduates in maths, physics or computer science as post-grads. I can teach a physicist how forests work, but it’s much harder to teach a biology student how to set up a directed percolation model.

Confessions of a former creationist


Still from Rise of the Planet of the Apes (2011).

I used to be a creationist. I have no qualms about admitting this now, despite being an established academic ecologist. I teach evolution at university, have written a textbook in which evolution is simply an accepted fact, and have donated to campaigns to teach evolution to schoolchildren. I’m not ashamed of my past, partly because there’s no point, but mostly because I still remember how creationism fit into a wider pattern of beliefs and attitudes that I once held. Evolution is scientifically, factually, demonstrably true. But at the time, for me, divine creation was The Truth.

This post is an attempt to explain how my background allows me to remain sympathetic towards creationists, and to help others from more secular or scientific backgrounds to understand how a creationist worldview can persist despite such overwhelming and widely-available evidence to the contrary.

I grew up in a fundamentalist Christian church. Which one is immaterial — there are many similar religious groups across the world, and they are not exclusive to Christianity. What they share is a collective desire to inculcate the children of their members in a specific set of beliefs. Mine was regressive in many ways; women had to wear hats in the church and were excluded from any formal roles. It has taken many years to realise how these features of my upbringing, which I accepted as normal practice, shaped attitudes in my later life that I have fought hard to correct. Perhaps this can be a subject for a future post. But one clear message, delivered from lay preachers at the pulpit, from Sunday School teachers, from the in-house literature laid out for our edification, was that evolution was a lie.*

The vehemence with which evolution was rejected was derived from a foundational belief in absolute Biblical truth. This didn’t quite go so far as a strictly literal interpretation: not all members of the church thought that creation took place in six days, and the extreme positions of Young Earth creationism were rarely advanced. But the Genesis account contained several features that were inconsistent with evolutionary theory, particularly in the order of appearance of different life-forms, or the idea that all species were created simultaneously. Most importantly, it conflicted with the separate creation of Adam as the first human, and of Eve as being formed from his flesh.** From an early age it was drilled into me that the Bible was the first authority, and evidence that did not fit was inherently suspect.

I recall being startled that so many people were willing to swallow the lie that was evolution. This genuinely perplexed me; what was in it for them? I don’t recall any cognitive dissonance over the overwhelming evidence in favour of evolution, mainly because I didn’t hear it, or look for it, and most likely would have ignored it anyway. One evening that has lived long in my memory was when our church held a ‘debate’ about evolution. In the absence of anyone willing to make a case for evolution, my father and I were enlisted to act as Devil’s advocates. That we were entirely unable to muster a coherent argument illustrates the depth of our ignorance at the time.***

Another feature of our church, and indeed of many non-conformist sects, was a confrontational approach to debate. We were trained in this, even taught to expect it when defending our beliefs. Differences of opinion within in the church were usually resolved by the open setting out of arguments and persuasion, rather than by respectful listening and thoughtful contemplation. In argument I am a belligerent opponent, not averse to deploying a battery of dirty rhetorical tricks to sway an audience. On the other hand, once persuaded of a case, I can be a strident ally. I know full well that this is not one of my most endearing personality traits.

What this meant was that the concept of being set against the world and its lies was impressed upon us at an early age. It was almost a heroic mission. At school as a late teenager I thought nothing of confronting my teacher when evolution was considered, turning one particular class into a fractious dispute. Who knows what the rest of the class thought; they were kind enough not to tell me.**** To my teenage mind, I was simply standing up for my beliefs, and being a lone voice only increased the responsibility I felt to hold my ground.

At the time the school syllabus in the UK contained very little evolution; it may be central to biology but the majority of the content was narrowly factual. It was entirely possible to get through school with straight-As in science while denying evolution entirely. I know because I did. Right up until I arrived at the University of Cambridge to study a degree in Natural Sciences. I reached the pinnacle of academic achievement within the UK educational system, and walked into the gates of Trinity College at the age of 18 still an ardent creationist.

My Damascene conversion came quickly, but it was not caused by losing an argument with a more experienced opponent, hearing a case against creationism, or even for that matter encountering one in favour of evolution. It came as I was exposed to a semester of lectures and laboratory practicals on invertebrate anatomy and physiology by Richard Barnes (our textbook was the magnificent Barnes et al.). He methodically outlined the structures of organisms, their development and the linkages among them. I don’t recall him ever even mentioning that this was magnificent evidence for evolution over creationism. He didn’t need to: it was obvious.

Halfway through the semester I got into another argument, only this time the tables had turned. In the church I was attending in Cambridge, I tackled a speaker on the subject of evolution, armed with only a few weeks of first-year undergraduate knowledge. I was a lone voice. This did not dissuade me. Looking back what is most striking is that, within 12 months, I had entirely switched corners, but was still quite willing to take on the whole room against established authority. Plus ca change…

That argument was particularly vitriolic, and led to me leaving the congregation. For some time afterwards, members of the church would track me down to explain the errors of my ways, but I never went back. It started a three-year journey that led, eventually, to my leaving religion altogether and becoming a firm atheist. It is a position I have held, against the views of most of my family and childhood friends, for nearly 20 years. I believe in humanism now as strongly as I ever believed in Christianity, and I will stand toe-to-toe with anyone on the topic. But my arguments are more securely formed for having the experience of once taken the other side and been entirely committed to it. I have fought with myself and, while one side won, I can still hear the other.

Here is where I think many fellow scientists, sceptics and rationalists can learn a trick, because there are many who simply find the creationist perspective as incomprehensible as I once found theirs. If you were raised in a secular household then you may never have met the arguments raised against evolution, and treat those who hold them as ignorant dinosaurs. If your knowledge of evolution is based solely on the high-school syllabus and received truth from scientific authority figures then, quite frankly, you’re not fully equipped to enter a debate on the subject with a well-prepared adversary.

To conclude, here are some lessons from my experience which may help in thinking about tackling entrenched, anti-scientific attitudes such as creationism.

Don’t bother getting into an argument with a committed creationist. Someone who holds creationist views based on their religion will not back down, even when outnumbered and in a corner. They have been trained to expect this. Ridicule, exasperation and insult are never effective tactics for persuasion, but actually the debate in itself usually won’t be sufficient either (for your opponent at least, although you can still win over an audience). A calm presentation of evidence is usually more effective. It is unlikely that they have ever been exposed to the facts supporting your case. Suggest to them that, in order to better understand what they’re objecting to, they should read one of the many introductions to evolutionary biology, then invite them to come back and discuss it at a later date. Out of politeness you might agree to do the same (and you can probably guess which it will be).

If you teach biology in Higher Education then you have creationist students. This is a simple statement of fact. In my twelve years of teaching at the University of Nottingham I’ve known of several; many more have no doubt kept their heads down. Insulting creationists for cheap laughs in lectures is unlikely to do anything to persuade them (sadly I haven’t been above this myself); more likely they will stop coming to your lectures. I would advocate not even mentioning creationism at all. Let evolution permeate your teaching, and eventually it will filter through to any thoughtful student.

Most of all, don’t look down on creationists. They are not ignorant, nor stupid, although they may be misinformed (wilfully or otherwise). They are often highly intelligent people whose opinions are internally consistent, and whose arguments are coherent, but derived from a different set of authorities to your own. Evolution is often rejected because it is perceived as a challenge to this framework, even if not a fundamental element. You will achieve more by finding ways to make evolution fit within their existing mindset than attempting to bring the whole structure down.***** Realising that evolution is true is revelatory and inspiring, but to accept this, your listener has to be convinced that it isn’t a threat. Otherwise you will only encounter an aggressive defence.


* One visiting speaker to our youth group made the case that dinosaur bones had been placed in the earth to give a 6000-year-old Earth an illusion of history; in other words, God had placed them there to test and deceive us. He got short shrift from many of us, but the point is that he was invited in the first place. It’s an old lie, but somewhere in your local town, I’m prepared to bet that children are still hearing it to this day.

** It is ironic that misrepresentations of scientific evidence, such as ‘mitochondrial Eve’ or ‘Adam’s Y chromosome’, have in recent years become an established part of attempts to defend the biblical account. Creationists are not averse to adopting the language of science when it fits their overall narrative.

*** To his credit, and partly as a result of taking an interest in both science in general and what his children do do, my father has since changed his mind.

**** A factor in this was that there were two biology teachers at our school, and one of them was a creationist. During my final few years he was away for long periods, but he had a continuing influence on me. On the one hand, I can genuinely thank him for inspiring me to study biology. Nevertheless, even in his absence, he gave me confidence that there was a scientific case for creationism.

***** There are of course many religious scientists who have no problem with evolutionary theory. I have several colleagues who are committed Christians, and suffer no cognitive dissonance as a result, despite the assumption by many hardline sceptics that they should. In this I would only note that we all hold internally contradictory positions on a range of topics; perhaps your weak spot is in politics or educational theory. I’m sure that I have plenty.

How to avoid the Allee effect, assuming that you’re a tree. Or a barnacle.

The Allee effect is familiar to anyone working in conservation, often colloquially described as the phenomenon whereby at low densities, populations become more vulnerable to extinction. This contradicts one of the assumptions of basic population models, which is that when competition for resources is low, populations should grow quickly. Instead this advantage is overcome by other factors, such as the difficulty in finding mates, or in resisting predation.*

More strictly, Allee effects are defined as positive density dependence in populations, that is to say, where increasing population density actually increases the fitness of individuals. When Allee effects are strong, they can result in populations shrinking in size when they’re below a critical level known as the Allee threshold. Above this point, the population will grow until eventually competition takes over and it reaches its carrying capacity (the equilibrium at which births and deaths are exactly in balance). Below the Allee threshold, the population shrinks and will inevitably go extinct. In conservation this is a bad thing, but if you’re trying to control an invasive species or a crop pest then it can be very helpful. Allee effects are therefore extremely important in applied ecology.


The growth rate of populations varies with their density. At high densities competition for resources causes the population to settle on a stable equilibrium known as the carrying capacity. At low densities the population slips beneath the Allee threshold and starts shrinking.

That’s how it works in theory. But in my research over the last few years, working with Jorge Velazquez, we’ve been examining how these simple population models respond when you take into account the spatial patterning of populations. Most individual organisms are not distributed regularly across habitats. Instead, they are often clustered, which means that from the perspective of an individual, the actual population density it experiences is higher than the average for the habitat as a whole. If individuals are spread out (perhaps in territories) then the opposite will be true.

This becomes important because species vary in the range over which they can do important things such as mate or disperse their offspring. A tree such as silver fir is wind-pollinated, and therefore effectively unlimited in the distance over which it can mate with other trees. Its seeds, however, are large and don’t travel anywhere near as far. In other words, it mates over longer distances than it disperses. Other trees, such as dipterocarps, are pollinated by insects which are unable to fly very far, and also have massive fruits that mostly fall right next to their parents. They are limited in both mating and dispersal.

Jorge and I had the idea that this difference in the ranges over which individuals could mate or disperse might affect their vulnerability to Allee effects. The missing element, however, was finding a species that could disperse over long distances but only mated over a short range. I couldn’t think of a tree with those characteristics**, but another organism I’ve worked on was ideal — barnacles!


In our new paper in Ecological Modelling we show that this variation in relative ranges of mating and dispersal changes the behaviour of whole populations, and makes some species more sensitive to Allee effects than others. We first show the principle mathematically, then demonstrate it using models for each of the three species above.

Fir trees don’t have any particular problems at low densities, although once populations build up they compete strongly for space because they can’t disperse their offspring very far. Dipterocarps, on the other hand, benefit from being clustered, because this makes it more likely that they will be able to find a mate.*** Their Allee threshold goes down; in other words, they are more tolerant of low population densities, and even of high mortality rates, as might occur if there is harvesting of trees. This benefit occurs despite competition for space within clusters.

Barnacles are an odd case because, although they don’t move during their adult life, their larvae are widely dispersed in the water. Nevertheless, barnacle larvae don’t just wash up on rocks randomly. They decide which areas to settle in, and once they find a suitable location, they move to be closer to other barnacles. In other words, barnacles deliberately cluster. This gives them the best of both worlds: they can escape competition from their parents, but benefit from the physical proximity required to reproduce. Their Allee threshold drops even further and their populations are highly resilient.

Measuring the ranges over which species can mate or disperse can have important implications in conservation and applied ecology. It’s not just a matter of having more accurate models; these principles could be used to identify species with particular combinations of traits which cause them to be vulnerable to Allee effects, and thereby make conservation of rare species more effective. Our models show that when finding a mate is the greatest challenge faced by an organism, increasing their clustering boosts the resilience and persistence of their populations. This trick might turn out to be very useful.

Velazquez-Castro J & Eichhorn MP (2017). Relative ranges of mating and dispersal modulate Allee thresholds in sessile species. Ecological Modelling 359, 269–275.

* It’s sometimes said that random fluctuations in small populations (e.g. in sex ratio) that increase their probabilities of extinction are Allee effects. I don’t agree that demographic stochasticity should be included because it doesn’t alter individual fitness.

** Please let me know if you can! Perhaps there’s a species with tiny pollinators but which is animal-dispersed. My expectation is that this should be a very rare combination of traits because their populations would be very unstable, and I’d be interested to see if any species can manage it.

*** If you’re wondering whether this might cause inbreeding, then that’s a reasonable question, but the answer isn’t straightforward. There is some evidence that species with poor pollen dispersal are more tolerant of inbreeding, which would reduce the apparent costs. There might be a complex evolutionary relationship between dispersal mode and inbreeding tolerance which is something to consider another time.

Unsavoury scientific pasts

This weekend I wrote an article for the BES Bulletin in which I referred to an intriguing character, Otto Schultz-Kampfhenkel (1910–1989). He was a German geographer, explorer and film-maker, whose lasting legacy was to have founded an institute producing educational films for schools on global matters (it still does). He also established a field centre in Portugal where I’ve taught and carried out some research, which is how his name first came to my attention.

Schultz-Kampfhenkel was well-known for his 1933 book Das Dschungel rief (The Jungle Cried), based on his expedition to Liberia, and a film Rätsel der Urwaldhölle (Riddle of the Jungle) from his 1937–37 expedition on the Amazon. Both are very much products of their time and, while no doubt valuable for their anthropological records and natural history observations, they are likely to be uncomfortable for modern audiences. One of the main reasons for this is that Schultz-Kampfhenkel was a Nazi.


A photo from the 1935–37 expedition on the Brazilian Amazon. I can find no evidence that Schultz-Kampfhenkel appears in this image; only that this was the team which he led, and clearly the flag that they carried.

Examining the careers of European cultural, academic and scientific figures of the mid-20th century always carries some trepidation. Many made compromises in order to protect themselves or their families; others found ways to manipulate the system to advance their own interests, regardless of their own personal affinities. My own family history contains examples, and it’s important to not make too many moral judgements from a distance that is now not only historical but also social and cultural. We cannot know how we would have acted in such circumstances; go back far enough and all of us are descended from murderers.

Such equivocation is unnecessary with Schultz-Kampfhenkel, who by all accounts appears to have been an enthusiastic fascist and collaborator with the wartime regime. One of his core activities was to set up a group of scientists to advise the German war effort. This included geologists, geographers, environmental scientists, foresters and, to my surprise, a botanist: Heinz Ellenberg (1913–1997), one the foremost vegetation ecologists of the mid-20th century. His works on the formation and classification of plant communities remain some of the most important contributions in the history of the field. Together they produced military maps for assessment of terrain and landscapes, based on both aerial photography and field surveys.

We of course know more of Ellenberg from his later career; after the war he worked with  Heinrich Walter in Stuttgart-Hohenheim*, and was later appointed as director of the Geobotanical Institute at ETH Zurich where he led the conceptual development of UNESCO’s Man and the Biosphere (MAB) programme, one of the most transformative innovations in conservation policy. To my mind, however, Ellenberg’s greatest contribution was the book Vegetation Mitteleuropas mit den Alpen in ökologischer, dynamischer und historischer Sicht (first edition 1963, with the last produced by Ellenberg himself in 1996). This has sat on my bookshelf (in translation) for 20 years now, and I still periodically refer to it as a trove of observations, measurements and insights. There is so much data in there that would be unpublishable in the modern world, even unthinkable that someone would bother to collect it (or to fund efforts to do so), and yet, as time goes on, this record of the vegetation of Europe in the 20th century becomes ever more valuable.

Why does Ellenberg’s name on the list of distinguished academic contributors to the German war effort matter? Perhaps it shouldn’t. Scientific facts are not in themselves political, even if scientists themselves are, as is often their funding, as well as the uses to which their work is put. Stripped of its political motivations, we can still learn from studies arising from even the most distasteful of sources. More to the point, Ellenberg’s most important academic contributions all came long after the war. I know a number of emeritus vegetation ecologists in Germany and the UK who must have met Ellenberg in person. Some of them even worked with him. Perhaps my discovery would not be news to them; they could even provide some clarificatory context to assuage my discomfort. Or, as with many of that generation, maybe it never came up in conversation.

Perhaps I shouldn’t be shocked to find this skeleton in Ellenberg’s closet, although what surprises me more is not that a man of his age was involved in the war effort, but rather that it was in his capacity as plant ecologist. I have my own strong political opinions as a socialist and committed anti-fascist. I’d like to think that none of this inflects my work (at least not in content, although whether it does in conduct is a different matter). Nor would I expect anyone reading my work to judge its value through that prism. Nevertheless, were there some way in which I could use my expertise to advance the causes I believe in, I would have no hesitation**.  None of us are only scientists. Was the same true of Ellenberg?

Learning the about the histories of influential scientists can have mixed results. Some have risen in my estimation as I’ve discovered more about their exploits (like the legendary botanist Richard Evan Schultes); others I can continue to admire while not wishing to spend any time in their company (see the recent Robert Trivers autobiography), while some turn out to have been surprisingly boring. We care about them as people because we are social creatures (mostly), but this should have no bearing on our estimation of their contributions to science. Nevertheless, however hard I try to rationalise it away, finding Ellenberg’s name on such a list has left a bad taste in my mouth. One of the giants of the field just became, for me, much shorter.

* Walter’s foundational work from the 1970s Die Vegetation der Erde in Öko-physiologischer Betrachtung was still core reading when I was an undergraduate in the 90s, and remains in print in the form of Breckle’s much-updated edition.

** I don’t see right now how my work on forest structural organisation is going to lead to a radical rebalancing of the social contract between our government its people, but if you can see a way then let me know, and quickly — we have an election coming up.