Tag Archives: population

The Greens need coherent policies on population and immigration Updated for 2026





Those famous electoral TV debates are getting closer – and it’s intriguing to imagine the dialogue between UKIP leader Nigel Farage and the Green leader Natalie Bennett.

One big area of disagreement is of course immigration, and the Greens’ immigration policy is, in their own words “liberal” – which in practice means absolutely no constraint or restriction on who enters the or stays in the UK.

Specifically, the Green Party “will progressively reduce UK immigration controls” and give non-Europeans the same free-movement rights as Europeans. That is, everyone is free to move in.

In my opinion, Bennett will struggle to defend this policy in debate with the populist Mr Farage, given the large scale immigration it would be certain to provoke if implemented any time soon. Even committed Greens will find it unrealistic – except as a very long term aspiration.

More cynically – has the Green Party given any thought to what the electoral consequences will be when their open door policy becomes widely known? As Mr Farage will surely make sure it does?

People look to the Greens for the promise of a long-term sustainable future for their descendants and the UK, as well as the Earth itself. So a policy that appears to actively negate that aspiration – by encouraging overpopulation and cultural instability – must undermine the party’s credibility in many voters’ eyes.

The population question

As a green (Oxford Ecology Movement) candidate in the 1979 general election I can quote our policy at the time: “The national aim is a replacement birth-rate in the short term, followed by a gradual reduction over the next 1 or 2 centuries to 20-30 million in Britain, achieved through education and popular consent.”

The Green population policy today is less specific, worthy but lacking in substance –  focussed more on global than UK issues, which enables the more political and controversial issue of the UK population (and the link to immigration) to be fudged.

The main thrust appears to be that we’ll need to look at population at some undefined future date (PP101, 103), but in the meantime we can have as many children as we like (PP106) and let everyone in who wants to come (PP111), provided we keep half an eye on “economic and environmental pressures”.

It is all very vague and woolly, and while it implies the need for an eventual limit, there is no thinking about what a sustainable population for the UK might be, thus also no means to achieve it, even if lip-service is paid to population being a proper subject of public debate (PP107).

There is a medium-term aim (PP120) “to promote debate on sustainable population levels for the UK ­ … to increase awareness of the issues not to set specific population targets.” But to discuss a sustainable population for the UK without having any idea of what you are aiming at seems, for a Green policy, worse than pointless.

Surely the essence of the green approach to life and humanity is long-term sustainability? So difficult issues like actual numbers and how to achieve them need to be openly and clearly discussed.

The emphasis is however on world population limits. Indeed some local Greens have suggested to me that as long as the total world population is stabilised, it doesn’t matter how people are distributed. So it’s OK for lots of people to flood into nice rich UK as this will result in fewer poor people somewhere else.

So apparently we should ignore our own interests in order to altruistically solve those of others currently less fortunate. It’s a noble wish, but surely each country needs to have policies that at least safeguard their own viability?

The debate must be allowed to take place

Fortunately the Green population debate is far from over. In recent posts on The Ecologist, Biff Vernon has argued for a population policy by stealth focussed on women’s status and health in poor countries, while Simon Ross from Population Matters argued that evading the core issue is dishonest and that in any case we have issues here in the UK.

Rupert Read, the Green prosective candidate for Cambridge, has also thrown his hat in the ring, in an Ecologist article that outright opposes mass immigration: We Greens need to be absolutely and resolutely pro-immigrant – while turning against large-scale immigration.

The Ecologist‘s founding editor Edward Goldsmith would probably have sided with Read and Ross. As he wrote in 1989 in ‘The population explosion‘, “A growing population is not intolerable per se but because of the increasing impact it must have on the natural environment. This impact is greatly magnified by the increase in material consumption made possible by economic development.”

But not only does the Green Party today have no coherent population policy, there is a campaign within the party to denigrate and censor the one UK organisation that does, Population Matters.

Already banned from advertising in Green World, the activist promoting this exclusion, Adam Ramsay, has also recently persuaded my local party in Oxfordshire to prevent Population Matters from having a stall at our annual Green Fair, a popular fund-raising event held in December, with stalls from all manner of ethical-ish small traders, wildlife/animal welfare groups, and various right-on campaigning groups.

Ramsay’s views are online on two blogposts on Green European Journal and Bright Green Scotland with vigorous counter-argument and comments under each, taken up also by Derek Wall on Another Green World.

Ramsay’s arguments at the Oxford meeting were emotive – he invoked supposed population bogeyman Thomas Malthus (see Wikipedia for a balanced view), the 19th century Irish potato famine, a Swiss population group using the term ‘lebensraum‘ (‘living space, biosphere’, but used by Nazis and therefore bad).

And all that before he finally got round to two of Population Matters’ policies that are said to clash with what is acceptable to the Green Party: means-tested benefit on 3+ children and “no net immigration”.

Natural partners, not enemies

Apart from the two policies just mentioned, Population Matters’ aims closely match those of the Green Party – resources, pollution, energy usage etc – so why not try to work together?

In their 2015 manifesto Population Matters specifically state that they don’t want to increase poverty, hence their 3-child policy is flexible, and “no net immigration” isn’t a ban on immigrants as opponents like to make out, but an attempt to limit immigration to the numbers leaving, currently over 300,000 annually!

Thus there is plenty of room to ‘agree to differ’ on these themes, and in any case, as already discussed, I would suggest the Green Party needs to take a long hard look at their own shortcomings in this area. Most particularly there is no defensible case for the censorship and bans that these campaigners are so keen to enforce.

The Oxfordshire party has 700 members, but the decision was taken at a business meeting attended by about 25 people, with 12 voting for the ban, 5 against and several abstentions. Should important decisions affecting potential allies be taken so cavalierly ?

Both immigration and population are widely misunderstood. Immigration, or rather calls for it to be curtailed, is all too often seen in a racial or racist context. Clearly that motivates some, but we should not all be tarred with that brush – from a sustainability perspective, it makes no difference whatever what colour, race or religion extra people are.

They are, simply, people – and with our 413 people per square kilometre, England has recently overtaken The Netherlands as the most densely populated country in Europe – excluding city states. Wales, Northern Ireland and especially Scotland are less heavily settled.

For a long-term future any country needs to be fundamentally self-sufficient in food – we shouldn’t have to rely on imports, as in the long run there may not be surpluses available to buy – though exchanges are of course acceptable. Oats for bananas, anyone?

At present UK population levels this would only be possible if a lot more grain went into people’s mouths rather than meat animals, or a lot more land was (re)converted to high-intensity arable, itself unsustainable long-term. Also we have a responsibility to the planet’s other life, so we need wild space for both that life and for our own wellbeing.

Hence ever-increasing overcrowding is not desirable. I have heard local Greens pointing out that as there are some places more densely settled than England, then we can take more people. But that begs the question – why should we? do we want to? what good will it do us?

We can’t just wait for the global ‘demographic transition’

I’m not for a moment suggesting that population should elbow out the other major issues facing us all – ecosystem destruction, per capita consumption and related CO2 emissions and other pollution being obviously among the most serious, with their additive impacts on global warming and climate change.

However tackling the consumption / pollution aspects without including the population factor smacks of wilful blindness to the facts. The ‘demographic transition’, whereby increasing affluence reduces birth rates, has no doubt delayed the crunch point, but more importantly has lulled people into a false sense that population will somehow solve itself if we can sort out poverty across the planet.

Goldsmith was in fact trenchant on that point: “To seek to reduce population by systematically encouraging economic development is thus self-defeating since it can only increase natural consumption and thus environmental destructiveness.”

And it shouldn’t be forgotten that most of the last century’s massive world population growth arose from medical advances reducing infant and other death rates, not from increasing birth rates. It therefore makes sense to actively encourage a balancing reduction in birth rate, something that is a cultural block in many places.

Some cultures have responded quite rapidly with a demographic transition, but others, Egypt for example, have failed to do so, producing populations dramatically unbalanced with disproportionate numbers of young people and numerous negative knock-on effects from that including unemployment and wider disaffection.

In some developed countries like Japan and Italy where birth-rates have dropped, there is panic in conventional economics about the opposite problem: a preponderance of the elderly, seen as dependent on the workforce.

Hence there is a tendency to promote pro-natalist policies, or increased immigration, to offset the numbers of pensioners. In practice this is what has been happening in the UK, as millions of immigrants have flowed in over recent decades, many from Asia or Africa bringing in addition a tendency to higher birth-rates.

Having your cake and eating it

The Green Party rightly opposes “economic order that supposes the need for an ever-growing younger population to support the retired” (PP114) yet supports unrestricted immigration and “that the number of children people have should be a matter of free choice” (PP106).

But this is having your cake and eating it. There is ample evidence that increasing population exacerbates the already severe human impacts on the environment and the planet’s carrying capacity. Indeed as Jonathan Porritt points out,

“we are already using 50% more resources than the Earth can sustainably provide, and unless we change course very fast indeed, even two planet Earths will not be enough to meet our burgeoning economic demands (on a business-as-usual basis) by 2030.”

Addressing consumption alone is only taking half-measures, and won’t stop the crunch. There are limits to growth, both economically and in population – why are we still ignoring these when the basic issues were thrashed out ad nauseam in the 1970s, not least by Goldsmith.

We don’t know exactly where these limits are, and finding out should be a priority, but with ‘known unknowns’ it is advisable to follow the precautionary principle, particularly when its the one and only home planet that is at issue!

And the Green Party should not be afraid to say so!

 


 

Anthony Cheke is a retired sometime professional ecologist and later bookseller. Author of ‘Lost Land of the Dodo, an ecological history of Mauritius, Réunion & Rodrigues’. Green parliamentary candidate in the old Oxford constituency as a co-founder in 1979 of the Oxford Ecology Movement, formed to contest that year’s general election largely as a consciousness raising exercise (and then deliberately disbanded). We were to the left of the then Ecology Party and developed the ‘citizen’s income’ later adopted by the Green Party, and stressed the importance of reducing inequality – going further than the recent book ‘The Spirit Level’ by recommending a range of roughly 3:1 for highest to lowest disposable incomes.

 




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Phenotypic effects of climate change Updated for 2026

Understanding how changes in the climate affect biological communities is essential in predicting the future size and composition of populations. However, accurate predictions pose a difficult challenge for researchers. For the majority of animal species it is not feasible or ethical to conduct experiments into how these populations will respond to a changing climate. To enable us to gain an insight into potential futures of a population under climatic change, we use a computational model. Specifically, we use an integral projection model to investigate how changes in the North Atlantic Oscillation will influence the body weight and population size of a population of Soay sheep. The North Atlantic Oscillation is a large scale weather pattern of temperature differences across the Atlantic Ocean, which alters the local weather patterns in the North Atlantic region. We used published predictions of the future values of the North Atlantic Oscillation for the 21st Century. By doing this we are able to project the response of the study population to climate change based on our current best projections of the future climate.

Soay

Our model results, presented in the Early View paper “Analysis of phenotypic change in relation to climatic drivers in a population of Soay sheep”,  suggest that a continued positive trend in the North Atlantic Oscillation (positive pressure difference between Iceland and the Azores), as predicted by the majority of models, will be accompanied by a decrease in the population size of the Soay sheep and an increase in mean body weight. These changes are likely caused by a loss of smaller individuals from the population due to higher mortality in the adverse winters (mild but wet and windy) associated with the positive North Atlantic Oscillation.

Using an integral projection model as we have in this study gives us a glimpse into the potential future of populations where experimentation is difficult, and can improve our understanding of how populations will respond to changing climatic conditions. Using published climate predictions within our model also allows such studies to be placed in the realm of current climate research and (importantly) our projections can be updated as new climate predictions are released.

Synthesising: Population genetics and tropical ecology Updated for 2026

This is our first collaboration study between a population geneticist, Hideki Innan, and a field-based tropical ecologist, me, Yayoi Takeuchi.
I have been long wondering why Hubbell’s neutral model fitted so well to tropical forest communities because my impression of the tropical forest was the opposite. When I was doing my postdoctoral work in Hideki’s lab, he got interested in this issue because Hubbell’s model is based on the theory of population genetics. As such we started working together on this topic, and I found that population genetics holds sophisticated and well-established theories and methodologies, which could be well applied to community ecology. We believe that incorporating those techniques will provide breakthrough insights to elucidate mechanisms shaping complex natural communities.

Yaoyoij

A species-rich tropical rain forest in Lambir Hills National Park in Sarawak, Malaysia. Photo by Yayoi Takeuchi

The study “Evaluating the performance of neutrality tests of a local community using a niche-structured simulation model” summarized:

Is your favorite local community really neutral? —- It might be “No”! Here, we found that two common methods to test Hubbell’s neutral model were not robust enough to reject neutrality.
Hubbell’s neutral model provides a good fit to the data from wide range of natural communities including tropical forests and coral reefs. There are two parameters in his model that are usually unknown and commonly estimated from the data to be tested. Two common methods to test Hubbell’s neutral model, the SAD-fitting approach and re-sampling approach, use these estimated parameters. To examine the performance of these tests, we developed a simple niche model which incorporates stochastic demography, and these two tests were applied to a simulated non-neutral data with niche-structured community. Our results suggested that these tests had relatively poor power to reject neutrality, simply due to overfitting of the neutral model with unrealistic estimated parameters. We also discussed how we could improve the performance in this paper.

Effects of population densities on invasiveness Updated for 2026

Invasive species have negative economic and environmental consequences worldwide and, in our changing world, it has become increasingly important to understand their impacts. However, when assessing the impacts of invasive species, scientists often compare un-invaded sites with highly invaded sites, representing the ‘worst-case scenario’. Consequently, there is little information on how the impact of invaders varies with their population size. In the Early View paper “Population density modifies the ecological impacts of invasive species” we use experimental ponds to assess how ecological impact varies across different population densities for a model invasive fish (Pseudorasbora parva).

Invading2

We examined the relationship between density and impact to develop density-impact curves (see attached figure). We found both linear and non-linear density-impact curves for different direct and indirect ecological impacts. For instance, the relationship between fish density and zooplankton biomass and abundance was a high-threshold curve, indicating a smaller impact than a linear relationship would predict.

IInvading3

We also found density-impact relationships that were linear, low-threshold or s-shaped. Therefore, we caution against
the common assumption that ecological impact increases linearly with invader density. An understanding of the relationship between invader population density and ecological impact can assist in developing realistic and sustainable management strategies for controlling the negative impacts of invaders.

The potential relationships between invasive population density and ecological impacts. Re-drawn from Yokomizo et al. (2009, Ecological Applications; DOI:10.1890/08-0442.1).

The potential relationships between invasive population density and
ecological impacts. Re-drawn from Yokomizo et al. (2009, Ecological
Applications; DOI:10.1890/08-0442.1).

Michelle C. Jackson and co-authors

White stork modelling Updated for 2026

Understanding lifetime tracks and fitness of long distance avian migrants. This is the title of our DFG-funded German-Israeli Project Cooperation and it is also our quest for several years. Within this project, we aim to explore how movement, survival and reproduction reflect an optimal response to the environment. Evidence is drawn from both theoretical and empirical analyses. Migrants like white storks are particularly interesting for studying these questions as they move large distances and may experience different environmental conditions in different parts of the world with more or less strong impacts on their fitness (carry-over effects). Small-scale movement and behavior and their impact on local population dynamics are equally interesting. Latest technologies allow us unprecedented insights into the life of animals. For example, ultra-light GPS tags allow tracking individuals with very high temporal resolution and over several years, and acceleration measurements allow classifying behavior from distinct acceleration signals. These data together with careful monitoring provide the means for better understanding movement phenomena and their consequences for population dynamics and fitness. Juni11 103 Mit_Sender

My main focus within the project are developing behavior-based models for different life-cycle stages (e.g. breeding, migrating, wintering) as well as annual-cycle models that allow studying carry-over effects on individual fitness and population dynamics. Thereby, optimality is an important topic. From evolutionary perspective, fitness-maximizing, optimal behavioral strategies should evolve, determining for example when an individual should start reproducing or start migrating within the annual cycle. On finer temporal and spatial resolution, optimal foraging strategies should evolve which are the focus of our study ‚Individual-based modeling of resource competition to predict density-dependent population dynamics: a case study with white storks‘ (Zurell et al.). Here, we aimed to better understand how density-dependent demographic rates may evolve from home range behavior. To this end, we built an individual-based model for foraging white storks that incorporates both physiology and behavior. We expected that the form of density dependence may differ between different home range behaviors. To our surprise, we also found that it may differ strongly between landscapes with the same degree of fragmentation and the same overall resource availability. This phenomenon is strongly affected by the behavioral trade-offs and by imperfect detection of resources. Thereby, simulated patterns corresponded surprisingly well to empirical patterns although the model was not calibrated. For predicting population or even community dynamics under changing environmental conditions, it seems crucial to better understand these interactive effects of behavior and local environment.

We heartily invite you to play around with the model code (available at http://www.wsl.ch/info/mitarbeitende/zurell/downloads_EN) and adapt it to your needs. As you will see, the model also allows exploring additional aspects of movement ecology, for example studying movement paths or density-dependent home range structures in more detail.