Collecting samples from a wire attached to a bear rub tree

The ethics of population studies

What you need to keep in mind when you’re researching populations

A population study is a scientific investigation that looks at a group of individual plants or animals of the same species living in a given area or habitat.

Biologists, geographers, ecologists and psychologists might use population studies to find out how individuals from a certain species interact with one another and with the environment. For instance, a marine biologist who wants to find out how a species of fish is affected by water pollution might use a population study to find out how many of the fish live in a polluted area compared to a non-polluted area. They could also measure other demographics (see ‘Demography dynamics’) of the population, such as the birth rate, and monitor how those characteristics change over time.

Population studies like this can help us spot when a species is headed towards extinction or if it is under threat from a change to its environment. It can also help us understand the behaviour and life cycle of a species, for instance its migration or breeding habits.

Research ethics

All scientific research should be designed and carried out in a way that upholds basic ethical principles. These principles are agreed by governing bodies or communities; sometimes they are international agreements. They set out the responsibilities of researchers to their subjects, colleagues and society, and describe important values that all researchers should protect.

Throughout the 20th century different people decided to set down the ethical principles that they believed scientists should uphold. The most recent example of a set of principles is the Belmont Report. The report was published in 1978 and took four years to produce. It describes the basic ethical principles for conducting research on human subjects, but its three key elements are useful for considering the ethics of all scientific research. They are:

Respect for persons:

  • acknowledge autonomy
  • protect those with diminished autonomy.


  • make efforts to secure the wellbeing of others
  • do not harm
  • maximise possible benefits and minimise possible harms.


  • burdens and benefits of research should be distributed fairly.

Some of the statements of ethical principles were created in response to significant high-profile incidences of unethical conduct. This page from Bryn Mawr College catalogues some of these, such as the Nazis’ medical experiments and the Tuskegee Syphilis Study.

To help researchers keep their work in line with ethical principles, many organisations produce their own sets of ethical guidelines, checklists of ‘dos and don’ts’ that set out the practical steps researchers should take to make sure that their research is ethical. Ethical guidelines protect the subjects of research, whether they are plants, animals or humans.

How does this apply to me?

If you are planning your own population study, you should spend some time thinking about the ethics of your research. Are there any parts of the study that may go against ethical principles? How could you change your plans to reduce the risk of this happening? Are there guidelines you could follow to help you design an ethical study?

Here are a few examples of how and why ethics are relevant to different population studies.


You might think that ethics are only relevant to studies involving animals and humans, but studies of plants can also raise ethical issues.

It is easier than ever before to travel around the world and to visit remote locations that would once have taken weeks to reach. This means more expeditions are being made, by more people, to the world’s wildernesses. Expeditions and fieldwork can help us to understand the natural world and to protect it; they often study rare or endangered species and can gather evidence to support conservation work. But fieldwork can also risk disrupting or damaging delicate habitats and plants.

Some studies might involve you collecting samples or plant specimens from the population you are researching, so that you can check that you have identified the plant properly in the field or study it in more detail in a laboratory. If this is not done responsibly it can damage plants or habitats and may even be against the law.

There are laws surrounding the transport of plants between different countries, and even in the UK some wild plants are specially protected, making it an offence to pick or cut them without a licence. So, it is important to think carefully before taking a sample from a plant; a photograph of the plant might be a better way to record what it looks like.


The ethics of using animals in scientific research, particularly for experimentation, are often debated by the scientific community, the media, animal rights campaigners and the wider public. Population studies look at animals in their natural environment, not in a laboratory, but there may still be ethical issues to consider.

To measure the size of a population (how many individual plants, animals or people there are in a given area) researchers usually count the number of individuals within a smaller sample area and then estimate the size of the full population using their sample. The challenge for researchers studying populations of animals is that many species are constantly on the move, which makes counting individuals accurately more difficult. It can also be hard to distinguish between different animals.

One way to estimate the size of a population of wild animals is to use the mark–release–recapture method. This method involves capturing a sample number of animals and marking them with, for instance, a tag, ring, tattoo or chip, before releasing them back into the population. By repeatedly trapping a number of animals at random and counting the number of tagged animals in each sample, researchers can estimate the size of a population and monitor whether it is increasing or decreasing.

Advances in microchipping and ultralight materials mean that animals can now be tagged without hindering their movement, risking injury or even leaving a visible mark, but there are still concerns that capturing and handling animals for this purpose can cause physical discomfort and psychological distress.

Population studies often play an important role in monitoring, conserving and protecting the animals that they study, so using methods such as the mark–release–recapture method can be justified by the benefits they will bring to the whole population in the longer term. But when conducting ethical studies you should always seek to minimise the harm and maximise the benefits of your research, which may mean considering an alternative method for taking the measurements you need or investing time and money to improve the method that you are using, so as to reduce the risk of distressing the animals involved.


Human population studies provide vital information for medical and social research. They can help us to understand how our population is changing (for example, why in the UK we have an ageing population), the impact and spread of disease (such as the AIDS epidemic in Africa), or the relation between human populations and the natural resources that support them. However, if such studies do not follow ethical principles and guidelines there can be very serious consequences for both their subjects and researchers. So, it is essential that research institutions, societies and governments have detailed ethical guidelines for research involving human subjects.

The first requirement set down by the Belmont Report is that all subjects in a study must give ‘informed consent’ to take part in the research. This means that not only should individuals have a choice over whether or not to take part in a study, but that they must be able to make that judgement based on a good understanding of how the study will be conducted, its purpose, and the risks and benefits that may come from taking part.

This may seem a simple requirement: does a subject agree to take part or not? But population studies often involve large numbers of subjects who may be spread across a large geographical area, and often there are individuals of all ages and abilities involved. In these circumstances making sure all your subjects consent to your study fully and freely can be a challenge.

Some groups of people, such as the very old or the very young, may not be able, or may find it hard, to make an informed decision. Language barriers and cultural differences can also make it difficult for researchers to communicate well with potential subjects. If a researcher is speaking to a subject via an interpreter for instance, it may be hard for them to know whether the individual has fully understood the nature of the study and their role in it.

Sometimes researchers may need to encourage subjects to volunteer; if they do, they may persuade a subject to take part or offer them an incentive, such as money. Researchers may regard this as necessary in order to deliver the longer-term benefit that their study will bring, but in some cases it might undermine an individual’s autonomy; there is a risk that a subject may be pressurised into taking part, or may agree without fully understanding the consequences.

Lead image:

Collecting hair samples from a tree rub hair snare.  This project used the barbed wire hair snag technique in conjunction with statistical models to estimate the number of grizzly bears in the area. DNA was extracted from from bear hair collected along survey routes and from systematically positioned hair snag stations.

Glacier NPS/Flickr CC BY

Questions for discussion

  • Imagine you are planning an expedition to study rare carnivorous plants in the Amazon rainforest. What would be the potential harm and benefits of your expedition? What steps could you take to reduce the impact of the expedition on the environment?
  • Imagine you are writing a set of guidelines for researchers who are studying human subjects. What guidelines would you include to make sure that a study supports the three ethical principles of autonomy, beneficence and justice?
  • Can you think of an alternative to the mark–release–recapture method for measuring the size of a population of animals? Research other methods that ecologists use to monitor populations of animals and make a list of their pros and cons. Do you think there is one method that is more ethical than the others?

Further reading

About this resource

This resource was first published in ‘Populations’ in June 2014.

Genetics and genomics
Education levels:
16–19, Continuing professional development