Population size | ConservationBytes.com

Keeping babies alive will lower population growth

23 02 2023

We’ve just published a paper in PLOS ONE showing high infant mortality rates are contributing to an incessant rise of the global human population, which supports arguments for greater access to contraception and family planning in low- and middle-income nations.

In collaboration with Melinda Judge, Chitra Saraswati, Claire Perry, Jane Heyworth, and Peter Le Souëf of the University of Western Australia‘s School of Medicine and the Telethon Kids Institute, we found that higher baby death rates and larger household sizes (as an indicator of population density) lead to higher fertility rates.

In the first study of its kind, we provide a compelling argument that the United Nations’ Sustainable Development Goals for reducing infant mortality can be accelerated by increasing access to family planning.

Although it sounds counterintuitive, higher baby death rates are linked to higher population growth because the more babies a women loses, the more children she is likely to have. Family planning, including access to quality contraception, enables women to plan pregnancies better and therefore reduce infant mortality to curb the so-called ‘replacement’, or ‘insurance’ effect.

We evaluated six conditions thought to influence a woman’s fertility — availability of family planning, quality of family planning, education, religion, mortality, and socio-economic conditions, across 64 low- to middle-income countries.

Specifically, we tested whether

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Tags: child mortality, children, contraception, family planning, fertility, human population size, overpopulation, population density, Population size, SDGs, Sustainable Development Goals, United Nations
Categories : Africa, Asia, Central America, education, ethics, gender, health, human overpopulation, poverty, sustainability

Conservation paradox – the pros and cons of recreational hunting

20 02 2021

The recovery of species such as mountain zebra (*Equus zebra*) was partly supported by the economic benefits generated by trophy hunting. © Dr Hayley Clements

Through the leadership of my long-time friend and collaborator, Enrico Di Minin of the Helsinki Lab of Interdisciplinary Conservation Science, as well as the co-leadership of my (now) new colleague, Dr Hayley Clements, I’m pleased to report our new paper in One Earth — ‘Consequences of recreational hunting for biodiversity conservation and livelihoods‘.

My father was a hunter, and by proxy so was I when I was a lad. I wasn’t really a ‘good’ hunter in the sense that I rarely bagged my quarry, but during my childhood not only did I fail to question the morality of recreational hunting, I really thought that in fact it was by and large an important cultural endeavour.

It’s interesting how conditioned we become as children, for I couldn’t possibly conceive of hunting a wild, indigenous species for my own personal satisfaction now. I find the process not only morally and ethically reprehensible, I also think that most species don’t need the extra stress in an already environmentally stressed world.

I admit that I do shoot invasive European rabbits and foxes on my small farm from time to time — to reduce the grazing and browsing pressure on my trees from the former, and the predation pressure on the chooks from the latter. Of course, we eat the rabbits, but I tend just to bury the foxes. My dual perspective on the general issue of hunting in a way mirrors the two sides of the recreational hunting issue we report in our latest paper.

Wild boar (*Sus scrofus*). Photo: Valentin Panzirsch, CC BY-SA 3.0 AT, via Wikimedia Commons

I want to be clear here that our paper focuses exclusively on recreational hunting, and especially the hunting of charismatic species for their trophies. The activity is more than just a little controversial, for it raises many ethical and moral concerns at the very least. Yet, recreational hunting is frequently suggested as a way to conserve nature and support local people’s livelihoods.

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Tags: extinction, hunting, Livelihoods, Population size, poverty, poverty alleviation, recreational hunting, social licence, trophy hunting
Categories : Africa, agriculture, animal welfare, biodiversity, bushmeat, conservation, decline, demography, ecology, economics, ecosystem, environmental economics, environmental policy, ethics, exploitation, governance, habitat loss, human-wildlife conflict, invasive species, mammal, management, poverty, preservationist, research, sustainability, threatened species

What immigration means for Australia’s climate-change policies

12 06 2016

After dipping my foot into the murky waters of human population demography a few years ago, I’m a little surprised that I find myself here again. But this time I’m not examining what the future of the global human population might be and what it could mean for our environment; instead, I’m focussing on Australia’s population future and its implications for our greenhouse-gas emissions trajectories.

Just published in Asia and the Pacific Policy Forum¹, my paper with long-time co-author Barry Brook is entitled Implications of Australia’s population policy for future greenhouse gas emissions targets. It deals with the sticky question of just how many people Australia can ‘afford’ to house. By ‘afford’ I mean several things, but most specifically in the context of this paper is by how much we need to reduce our per capita emissions to achieve future reduction targets under various immigration-rate scenarios.

In many ways Australia’s population is typical of other developed nations in that its intrinsic fertility (1.78 children/woman) is below replacement (which is itself ~ 2.1 children/female). Yet Australia’s population grew nearly twice (1.88×) as large from 1971 to 2014. It doesn’t take a genius to figure out that most of our population growth is due to net immigration.

In fact, between 2006 and 2014, Australia welcomed a net of 215,000 new people per year (this means that of all the permanent immigrants and emigrants, a ‘net’ of approximately 215,000 stayed each year), which represents about 1% of our total population size (that latter most likely just ticked over 24 million). Read the rest of this entry »

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Tags: Australia, carrying capacity, climate change, environment, fossil fuels, greenhouse gase, immigration, migration, Population size
Categories : Australia, biodiversity, carbon, carbon trading, climate change, climate shift, conservation, deforestation, environmental policy, human overpopulation

Parts a whole do not make

17 02 2012

I’m particularly proud of our latest paper for three main reasons: (1) Salva Herrando-Pérez, lead author and contributor-extraordinaire to CB, has worked extremely hard to get this one out; (2) it is published in a really good journal; and most importantly, (3) it’s the very first empirical demonstration over hundreds of species that just because you have a density effect on some vital rate (e.g., survival, fertility, dispersal), this in no way means you have any evidence at all for density dependence at the population level. Let us explain.

Quantifying variation in population size is an important element for explaining and predicting population dynamics. In models where a vital (demographic) rate responds to change in population size, those ‘density-dependent’ relationships are ecologically understood as being demographic signals of trophic and social interactions, such as parasitism, predation or competition for shelter, because the intensity of those interactions varies with population size.

In fact, density-dependent effects reflect the theoretical capacity of populations to adjust growth and rebound from low or high numbers – and so this concept has become an important metric in population management and conservation (Eberhardt et al. 2008). Read the rest of this entry »

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Tags: density, density dependence, density feedback, ecology, environment, Population, population growth, Population size
Categories : conservation, demography, mathematics, modelling

Classics: Effective population size ratio

27 04 2011

Here’s another concise Conservation Classic highlighted in our upcoming book chapter (see previous entries on this book). Today’s entry comes from a colleague of mine, Dick Frankham, who has literally written the book on conservation genetics. I’ve published with Dick a few times – absolutely lovely chap who really knows his field more than almost any other. It is a great pleasure to include one of his seminal works as a Conservation Classic.

This entry is highly related to our work on minimum viable population size, and the controversial SAFE index (more on that later).

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Although it had long been recognized that inbreeding and loss of genetic diversity were accentuated in small, isolated populations (Charlesworth & Charlesworth, 1987), genetic hazards were generally considered to be of less consequence to extinction risk than demographic and environmental stochasticity. Frankham (1995) helped overturn this viewpoint, using a meta-analysis to draw together comprehensive evidence on the ratio of genetically effective to actual population size (N_e:N). Read the rest of this entry »