Students view human population growth as a threat to biodiversity

In their curriculum, university students in biology and environmental sciences rarely learn how human population growth affects the environment, or discuss its role relative to other factors. Human activities are often dealt with in courses, but not population increase. One exception, described below, comes from a Swedish ecology class that learned about and discussed how population growth and other agents threaten biodiversity. Their exam included listing and assessing the threats, with some surprising results.  

By Frank Götmark

As one part of a larger ecology course at the University of Gothenburg, a lecture presented threats to species and ecosystems (including how scientists, conservation agencies and other actors try to protect ecosystems, species’ habitats, and endangered species). The teacher emphasized two threats of special importance: global growth of human consumption and of human population. The prominence of these two factors has been acknowledged, for instance by the Intergovernmental Panel on Climate Change (IPCC) for greenhouse emissions and in the recent Scientists’ Warning to Humanity, but they are rarely reported on by the media or discussed in schools (particularly so for the threat of population growth).

In the lecture, consumption and population were presented as ultimate underlying factors driving extinction of species and degrading ecosystems. Proximate immediate threat factors such as climate disruption, pollution, and clearing land for agriculture were also mentioned, and they were given much attention in other parts of the course, and in the students’ textbook.

In two group discussions during the lecture on ultimate factors, the students were instructed to consider 1) how consumption could be regulated and reduced, and 2) how human population growth could be reduced, stabilized and reversed. In a follow-up exercise later during the course, the students investigated in groups the ultimate and proximate factors posing threats to large mammals in five major global regions. This was done using the Red List from the International Union for the Conservation of Nature (IUCN).

As many as 25 percent of the world’s mammal species for which there are data are critically endangered (CR), the highest threat level on the Red List. This means a total of about 225 species or taxa. Only one other organism group, amphibians, has a higher proportion of CR species (due to a fungus spreading globally). IUCN lists proximate threat factors for the mammals, as well as ecological information. Other sources were also available for the students, including information about consumption and population growth in countries in each of the five regions. Each group presented two red-listed (CR) mammal species, their distribution, population sizes and trends, food, habitat and behavior, threat factors and what can be done to improve the situation for each species.

In the final exam, one question dealt with the lecture on ultimate and proximate threats, and the exercise about endangered mammals. The students had all course material available, including the textbook. The question had three parts:

“(a) Which proximate threat factors influence biodiversity and in particular the world’s endangered species? Suggest at least four factors.

(b)  Which ultimate threat factors influence biodiversity and in particular the world’s endangered species? Suggest at least two factors.

(c) Is it possible to rank threat factors in importance, to improve our knowledge and help safeguard biodiversity?”

Here is the result for question (a):

The dominating proximate threat factors suggested were hunting (including illegal hunting) and invasive species. Then followed agriculture, pollution, forest destruction, climate disruption, habitat destruction, resource extraction/energy and urbanization. A few students also listed overfishing, living space for humans, diseases, eutrophication, hydroelectric power dams and infrastructure, such as roads.

As might be expected, the result indicates that exercises during a course can strongly influence the answers given by students in the exam. “Hunting” was a reported common threat against the mammal species investigated, and “Invasive species” was the subject of a second large exercise during the course. Exercises apparently strongly affect the students’ memory of a course. However, the most general and correct answer to (a) should be “Habitat destruction”, to judge from the textbook. Many students also listed factors related to destruction of species’ habitats (e.g., agriculture and forest destruction, see graph).

Here is the result for question (b), on the ultimate threat factors:

The increase in the human population was the most common answer (64 students), followed by consumption increase (52), as ultimate threat factors. Pollution and climate (6) were probably regarded by most students as proximate factors, yet some of them listed it here. Making a living and earning money (6) is more of an underlying ultimate factor, as is economic growth (4) which strongly influences human consumption levels. Had the lecture and exercise emphasized only consumption and economy, the answers might have been dominated by the role of excessive consumption, often mentioned in the media. For example, the major Swedish newspaper ‘Dagens Nyheter’ in their ‘Greta-issue’ (6 Dec, 2020) focused entirely on global warming and consumption, even in the interview with David Attenborough on climate. Attenborough’s view on population growth should be well known, but the journalist didn’t ask about population increase.

A few students suggested other interesting factors as regards biodiversity and the threats to species, such as technical and medical advances (1), political instability (2), and “uninterest among people” (1).

Finally, question (c) asked students to rank, if possible, the relative importance of the threat factors. Here, all threat factors were to be considered. Many students wrote that ranking is not possible, since ultimate factors – the ones mainly discussed by them – are strongly related, and dependent on each other. One student wrote that the equation “Human environmental impact = number of people on Earth x average consumption per person” summarized it all well. However, some students did rank the factors, with the following result:

Among these answers, population increase and the distribution of people (30) were considered most important, followed by human consumption (5), suggested by surprisingly few students, overexploitation (4) and climate disruption (4). One or two students suggested other ultimate factors, such as modern lifestyle (2), the market economy (1), political corruption (1), and human selfishness (1).

The course covered ecology and biodiversity but also sustainable development, motivating a broad approach. The role of population growth for biodiversity was not clarified in other lectures and exercises in the course, or in the textbook. The ranking of population increase as a major threat factor by the students therefore was quite surprising.

Students judged human population growth and size as strongly contributing to the threat against endangered species. Thus, if given relevant information, students are openminded as regards the role of population growth in the biodiversity crisis, although this threat factor presently receives little attention in university courses, media and politics. Courses in biology and conservation at various educational levels need to take a broad approach, including all the main factors driving biodiversity loss – including changes in human population size.