Lecture 4: Impact of human population on environment

Added: 2026-05-09

[00:00:16]Hello dear learners, welcome to the course on environmental issues, challenges and management. I am Dr. Vishal Prasad, assistant professor at the Institute of Environment and Sustainable Development, Banaras Hindu University. Dear learners, welcome back to the course on environmental issues, challenges and management. This is week one module number one human environment and urbanization lecture number four impact of human population on environment. So this is what we are going to discuss today. What is human population growth and what are the impacts of increasing human population and environment with reference to resource depletion, environmental degradation and pollution, climate change and biodiversity loss, unsustainable land uses and we will then see some of the mitigation measures and the solutions for such problems created by the human population. So what is human population growth? Human population growth is the increase in number of people on earth. The number of people how it is increasing and the total number of people which is continuously increasing is nothing but the human population growth. And this particular feature of human population growth is driven by the factor of birth rate that exceeds death rate. If birth rate and death rate are same then there would be no human net no net human population growth. But what happens now that the birth rate has started increasing more than the death rate. And because of this increased birth rate the human population is continuously growing on this earth. This human population is also influenced by migration. But this impacts the population especially in the urban localities or the cities.

[00:02:05]Historically, population growth was slow but it accelerated dramatically due to advancements in public health, agriculture and medicine which lowered death rates. So you can see that advancements in public health, agriculture, medicine everything which increased this decreased the death rate and because of this decreased that threat birth rate escalated and became more than that of the death rate and that resulted in a net growth or population growth on this earth. So this growth has a significant impact on global resources and the environment.

[00:02:43]Presently go global population has reached around 8.2 billions in 2025 and it is expected to grow to around 9.6 billion by 2050.

[00:02:56]India alone is responsible for 1.5 billion people in the year 202425 and we have surpassed China also. So India is one of the biggest country or the first country in fact I would say most populous country in the world.

[00:03:21]India is one of the most populous country in the world right now. So you can see here these are some of the key factors which have led to the enormous population growth. Birth rate with respect to time birth rate has escalated with in comparison to the death rate.

[00:03:43]More infants are being born than what we are getting deceased. The mortality is reduced again because of the medical or health facilities.

[00:03:54]They are good good medical or health facilities which have reduced the death threat.

[00:04:03]Mortalities are have been reduced.

[00:04:05]Definitely we are becoming a food surplus economy.

[00:04:16]In most of the places in most of the countries increased food supply is very high. The fruit growth is very high because of which the birth rate is high because of which the mortality rate has declined because of which growth and the age of the people have increased. So another is migration. This basically impacts in cities as I said earlier in cities when migration is more towards the urban population the urban population tends to show a growth in number of people. In India, human population grew significantly from 1900 to present with the rate increasing dramatically after 1951. And as I said earlier around 1.4 billion people are there in India right now. This graph tries to show you uh this is just a picture not the exact figure just a picture to make you understand that how population has been increasing. There has been a steady increase in the population from 1900 to present. Earlier in the year from 1900 to 199 21 the there was a phase of stagnant population. Why? Because diseases were very high over there. Food shortages was there. World war was there and all these and all these led to death rate. More death, more mortality. There were no adequate medicine facilities or healthcare facilities which could have prevented people from dying. The food production was very low. So all these thing in in totality led to a great decline in the population along with the similar rate of birth. Then the year from 1921 to 2081 was seen to be as a rate of a stage of steady growth rate where the population was fairly stable.

[00:06:05]It didn't increased much neither it declined much. Then from 1981 until 2000 there was a population explosion. As you can see you explosion means blast was there. We increased steely like this. There was a very fast rate of increment in number of people and human population growth was seen to be very high. Somehow from 2011 high growth is still being maintained but the rates are slow. This is acceptable a bit. Human population growth as it increases it increases the pressure on the environment. And how? Through higher resource consumption. Whatever resources are there, the in more number of people will consume that same resource in a very less amount of time or less period of days. Greater waste generation. More the people more will be the waste generated.

[00:07:03]It is reciprocal. intensified land use.

[00:07:07]Lands are limited. Lands are limited and this limited land itself has to suffice the growing population.

[00:07:28]So if you think that the same piece of land has to supply food to 10 people, what pressure would be on it? And when the same piece of land has to supply food to 100 people, what extra pressure it will be bearing or extra burden it will be bearing. So these are all problems because of the increasing envir human population on the environment. Now this process of increasing human population and all these higher resource consumption, greater waste generation and intensif intensified use, land use leads to several problems like deforestation, water scarcity, pollution of air, water and soil, depletion of natural resources like minerals and fossil fuels, loss of biodiversity and contribution towards climate change. We will take them one by one. So some of the in impacts of increasing human population and environment has been seen as resource depletion as I was discussing that the resources are finite. If the same resource is being used by less number of people it will go carry on for ages. But if the same number of same amount of resource is being consumed by higher number of people then what will happen within days or within a very short period of time it will get vanished off.

[00:08:43]Environmental degradation. More the people, more the waste generated and more is the pollution caused. Climate change and biodiversity loss. Climate change more. Why? Because more the resources are being used, more greenhouse gases and more other pollutants are being emitted out which are leading to increase in or elevation in the global temperature. Biodiversity loss. We humans are continuously encroaching the natural habitats and destroying the habitats of the wild animals which cannot survive in the urban settlements. Unsustainable land uses land has being land is being used in an very unsustainable manner just as a means to sustain uh pro provide maximum amount of produce. So when we talk about resource depletion what we observe? We observe that in intensive resource consumption is there a growing population increases demand for finite natural resources like water, energy and raw materials. We know water can neither be created nor nor destroyed but its form can be changed and during this conversion of form it gets rendered into a unusable form for the humans and the as the human population incre is increasing its demand for water consumption is continuously increasing similar is the case for energy more the population more will be the demand for energy more the urban population more is the demand for urban energy and 24/7 energy we need for all our purposes.

[00:10:14]Continuous in energy input is required.

[00:10:17]Where will that energy come from? That energy is definitely coming from natural reserves in form of fossil fuel and other things which are present on this earth. Then raw materials, the minerals, soils and many other things which are required for production of crops, growth of humans are all finite. And if these finite things are continuously used without any check without any limitation with for the increasing population what will happen these are going to get vanished up get used up before time. So in some areas such intensive resource consumption leads to the over extraction of reservoir from reservoirs groundwater depletion and competition for the access.

[00:11:03]Next problem is of fossil fuel dependence. Increased energy demand especially in rapidly grow developing nations often results in a heavier reliance on fossil fuels which are detrimental due to greenhouse gas emission. So more the fossil fuel more will be the greenhouse gas emission and this dependency on fossil fuel will definitely increase because our energy demand is continuously increasing. Waste generation. More people produce more waste including seaweed, plastic, industrial garbage. This contributes to air, water and soil contamination which natural system cannot absorb and process indefinitely. So you can see a variety of waste is being there seage plastic industrial garbage and this is all being mixed and being dumped into any of the natural system which might be air, water or soil. Every natural system air water and soil has its own regeneration capacity. We are putting the garbage or the waste or the pollution beyond that its carrying capacity. So its regeneration will not be feasible after a certain time. Regeneration of good quality air or a good quality water or good quality soil. It needs a certain time and it can bear only a certain amount of toxicant or pollutant or contaminant burden of these things. But what we are doing with the advent of increasing population what happens because population is high the waste amount or the generated waste is also very high. So when such large piles of waste is generated what happens this particular thing n or the natural system cannot hold it and that becomes a problem. Urbanization and infrastructure strain is again a major challenge with increasing population. Urban setups are as here the factor of migration comes into picture as we discussed earlier what happens due to migration from rural to the urban setups the population size of urban setups increases. So as population grows cities expand concentrating waste and increasing resource consumption. Wastes are more generated and concentrated and in resource consumption increases it in a process known as urban sprawl. This can overwhelm or take upon infrastructure for water, sanitation and waste disposal. Infrastructure is not well equipped to hold that many population in the urban setups as the number of people are there present in a due to this urbanist. So here this picture shows you how increased resource consumption and scarcity can lead to a problem. You can see that the depletion of natural resources is continuously occurring.

[00:13:51]Why? Because more people require more food. They require more water. They require more energy. Housing housing is again a big challenge and materials leading to depletion of nonrenewable resources like fossil fuel and minerals.

[00:14:07]So if such kind of a things is going to be used up no more available what will happen the question is what will happen how the population is going to survive the one more thing is come you can see in this picture water water scarcity is a global problem now everywhere we are facing resources are at least available but global crisis of water is occurring what is happening at several places you can see there is law no water. People are purchasing water at such a high price just for drinking. So what is this? This is water scarcity. So the here you can see that growing demand for fresh water can lead it to its over extraction. Over extraction groundwater table has gone so down so down impacting ecosystems and making difficult to sustain populations especially in developing countries. populations will not be able to survive in de developing countries because they don't have that higher economy or that good economy to purchase costly water from developed countries or from other places. Neither they have good technologies to recycle water, process water and make good water from the waste water. So this picture illustrates a gives you a very good illustration that if you can see depletion of natural resources, water scarcity, increasing industrial pollution, increased urbanization and everything how the people are increasing number of people is increasing with for the finite sources how tough it would be for people. So if you can understand that if a person is standing last in the row when his number will come for this water and which is also very finite whether that last person sitting in the standing in the last row will ever be able to get the water for his surviving his needs I don't think so another problem with an increasing global population is or human population is environmental degradation and pollution these are all escalated increased Deforestation increased because we need more timber. We need more infrastructure for space for developing infrastructure.

[00:16:21]We know we need more urban setups.

[00:16:23]Pollution increase. More people more pollution.

[00:16:27]Simple reciprocal relation. habitat loss and encroachment by the humans.

[00:16:43]The habitats of the wild animals are being encroached continuously by the humans. So here this slide shows you how environmental degradation and pollution is being carried out by the humans. They are continuously doing the deforestation. The need for land for agriculture, housing and industry results in the loss of forest which are vital habitats and carbon sinks. These forests are nothing but the thing sinks for carbon which has been emitted in the past. These forests have taken up all that carbon and stored in itself. What we do? We simply for our own sake without understanding what will happen to the environment when the uh stored CO2 will be released into the environment. What will happen? Simply climate change will happen. Global warming will occur. Then habitat is lost. Pollution increased human activity generates waste and pollution contaminating air, water and soil and harming ecosystems and human health. You can see here the water ecosystem is completely being damaged.

[00:17:50]Fishes and other animals living in the freshwater or marine system will not be able to survive because of the added pollutants into that. They are not meant to live with those toxic chemicals which we are continuously dumping in these water bodies or marine ecosystem, freshwater ecosystem, whatever you can think of. Habitat loss. When this deforestation occur, what happens?

[00:18:15]Deforestation, urban sprawl and conversion of land for other uses destroy natural habitats threatening many terrestrial and aquatic species contribution to mass extinction. So this deforestation contributes regularly to the mass extinction of species. This is at the mass the extinction of the species that is at a much higher rate which might have occurred naturally.

[00:18:40]Under natural conditions also species do get lost from the ecosystems but that rate is very slow and it is definitely not so much obvious and newer species do come up regularly as older species get lost but due due to pollution due to deforestation the loss of species at a very fast rate and emergence of new species at is at a very very slow rate which is almost negligible. The biggest problem is increasing human population is climate change and biodiversity loss.

[00:19:13]Climate change is one of the buzzword these days because you can see increasing temperature, shooting temperature, rising sea level. These are all results of the climate. So higher the emissions, growing population combined with increased consumption.

[00:19:27]Growing population, increased consumption lead to higher greenhouse gas emission from sources like industrial activity, transportation and agriculture. This intensifies climate change in associated risk. Why? Because these greenhouse gases have the potential to hold the heat from the sun and because of that it is it causes the greenhouse gas effect which leads to overall warming of the environment or overall warming of the earth.

[00:19:59]Accelerated extinction rate as we have seen earlier habitat loss driven by the expansion of agriculture and urban areas is a primary cause of biodiversity loss.

[00:20:11]Current extinction rates are estimated to be 40 to 100 times higher than the natural background levels. As I was discussing earlier, current rates are much much higher than what would have happened naturally.

[00:20:24]Deforestation and desertification.

[00:20:27]The need for more agricultural land and raw materials leads to widespread deforestation. We need more land for agriculture. We need more raw materials in dry areas. What happens? Overg grazing and intensive farming can lead to soil degradation and desertification.

[00:20:44]Then habitat enroachment. This is again a very big challenge for with the increasing human population. Human expansion into natural areas. Natural areas. Humans need space to live. They need houses to live. So what happens?

[00:21:01]They start encroaching the areas where there were no human settlements. and humans expansion into natural areas can increase the likelihood of zoootic diseases. What are these? These are infectious diseases that pass from animals to humans. Like we have seen in the recent past COVID 19, Ebola is there, Zika is there. So these are some of the diseases which are due to viruses and they are transferred from animals to the humans. If humans start encroaching the areas where these animals are naturally living, this is how you can see what climate change is doing.

[00:21:37]Industries, vehicles, urbanization, everything is emitting out a lot lot of greenhouse gases. Higher population numbers are associated with increased consumption and reliance on fossil fuel.

[00:21:49]Reliance on fossil fuel which release more greenhouse gas into the atmosphere exasbating climate change. Carbon release. Deforestation releases carbon dioxide stored in trees further contributing to rising global temperature.

[00:22:09]Carbon dioxide captures heat and this captured heat with the carbon or at the with the carbon dioxide molecule what will it do? It will heat up the surrounding area where this concentration of carbon dioxide is continuously increased. Another problem with increasing human population is unsustainable land use. Agriculture and urbanization expansion of human settlements and agricultural land transform natural landscapes altering water cycles and impacting ecosystems. You can see what has happened with the numbers continuously increasing. You can see behind this how many rows would be under standing.

[00:22:57]Deforestation is there, overg grazing is there, urbanization, mechanized agriculture. Here you can see how it was earlier and after the increased population what has happened the ecosystem of has completely changed.

[00:23:12]When the ecosystem will change, how will the habitat be preserved? If the habitat is not preserved, what will happen?

[00:23:19]Every biodiversity or the species diversity will be declined. So if the species diversity declines, what happens? Interaction among the ecosystem declines. When the interaction declines, then the ecosystem services decline. And if the ecosystem services declines, the natural resilience of the ecosystem declines. And if the natural resilience declines it is very it becomes very much vulnerable to the damage caused by various factors may it be anthropogenic or natural. So what are the mitigations steps and what solutions do we have to tackle or to handle the overgrowing human population on this earth and most important the environmental problems related to the overgrowing population.

[00:24:06]So solutions to these environmental challenges require a multi-dimensional approach that addresses both population dynamics and consumption patterns. First is empowering women's and girls. It is very most important that women's and girls of the society are empowered.

[00:24:24]Education and access to reproductive health services including voluntary family planning are critical for slowing population growth. When women are empowered, fertility rates tend to decline which can have long-term benefits for the environment and for climate mitigation efforts. We all know that women's are almost 50% of the society and if they are empowered they are made to take decision then definitely the population problem is going to be solved to a certain shifting consumption habits. Reducing consumptions particularly in high income nation is essential for lessening the strain on global resources. We have to understand and regulate our consumption pattern according to our need not according to our greed. We should be wise enough to understand what actually we need and consume that much. If such consumption pattern is shifted towards a more sustainable manner or more sustainable pattern then definitely the overgrowing population is not going to pose that much burden on the agricultural land at this or for the food demand or for the raw material demand as it is currently techn we should move towards technologydriven sustainable development. Transitioning to sustainable practices in agriculture, waste manage and energy production is very very vital. Renewable energy, green technology and efficient resource use can help mitigate the environmental impact of human activities. Next is conservation and urban planning.

[00:25:59]protecting natural habitats which is conservation of natural lands and designing sustainable compact urban areas with efficient public transport can help manage resource consumption and environmental impact. When we conserve the natural resources and make urban setups compact enough so to handle or to hold larger population to cater the needs of the larger population then definitely to a c certain extent the problems arising due to increasing population or environmental problems due to increasing population can be managed.

[00:26:34]Here you can see the pictorial representation of these solutions. If the women are empowered or decision or they are involved in the decision making what will happen? They will take wiser decision on the their role for protecting the environment and will definitely help in managing the environment better taking a larger population together to solve the problem. If we consume wisely then definitely load on the environment will be lessened. If we move towards renewable energy sources like solar panels or windmill then definitely the nonrenewable fossil fuel will be hold up to a larger time. If we go for better urban planning then definitely the pressure on the cities due to increasing urban sprawl will be lessened. So in conclusion, human population growth significantly impacts the environment through resource depletion, pollution, habitat destruction and climate change leading to unsustainable demands on earth's ecosystem.

[00:27:40]So if the earth's ecosystem is disturbed due to increasing grow population, what will happen? How will the human survive on this earth ecosystem? This is a big question. Addressing the environmental impacts of population growth requires a multifaceted approach, including sustainable resource management, investment in renewable energy and policies that promote family planning and education to hold the increasing human population to a controlled rate is very necessary and that will definitely come through education. Education is one of the most important weapon to curtail the uh limitations or curtail the problems being increased due to increasing human population. So understanding the intricate relationship between population dynamics and environmental health is crucial for developing effective strategies to mitigate these impacts and ensure a sustainable future for the planet.

[00:28:46]Population dynamics versus environmental health. This relation is very intricate.

[00:28:51]how population dynamics is impacting the environment and how much population should be there in a given space and time for maintaining the environment in a sustainable manner. This dynamics or this relationship needs to be unders.

[00:29:07]These are some of the references for further reading in the field of human population with respect to its impact on environment. Thank you very much.