 India is the second most populous country in the world. But have you ever wondered what kind of an impact we as a population must have on the planet? If you look it up, Google will tell you that there are 1.4 billion of us in this country. That's our population size. But if we want to find out about our impact, then we must understand how crowded the nation is. So in this video we'll talk about the different ways we can estimate this crowd and their impact on the ecosystem. The crowdedness of a particular area is expressed as population density. Now you must have noticed that I have kind of written pop everywhere whenever I'm talking about population. Now this is just an abbreviated form. Given that pop is an actual word, please don't mix between the two. I'll just probably write it down here. So pop dot means population in this entire video. Just something to remember. So the crowdedness of any particular area that's what population density is. It's the number of individuals per square mile or per square kilometer of an area. Now a place may have a very high population size but not necessarily a very high population density. For example, the population size of Mumbai is 20 million but it is way more crowded than the population of Delhi which is about 32 million. The population density in Mumbai is 25,000 people or 25,000 individuals per kilometer square compared to Delhi which is a measly 10,000 individuals per kilometer square. If an area gets too crowded like how we saw it is like in Mumbai, then there will be a more fierce competition for land, water, energy and other natural resources. Such a kind of competition will negatively impact the environment and it may lead to things like deforestation and pollution. Ultimately having a severe impact on the ecosystem. Monitoring this impact allows us to take certain measures to improve living conditions and the ecosystems in that area. Like introducing proper waste disposal and proper sanitation to decrease pollution or switching to an alternative form of energy like solar energy instead of using timber and coal. That means population density of a place doesn't just tell us about the population status but also their impact on the natural resources and the ecosystem there and if any special action is required to reduce any negative impact on them. Now the population densities of places like Delhi and Mumbai can be measured by physically counting the number of individuals in those areas. But things get a little tricky when we try to physically count everything. Think about it. How will you count the number of all the tigers which are present in India? It's quite difficult and time-consuming not to mention extremely dangerous. So in this case we use an indirect approach of counting the tigers. Instead of seeking them out in the jungles we track their pug marks or their paw prints. Every tiger has a unique paw print. Experts can study these paw prints and figure out which individual tiger it belongs to and thus count the number. The paw prints are analyzed either by photographing them or tracing them on a glass plate and then they are studied thoroughly to identify the tiger. But this method kind of fell through because of its inaccuracy. Most of the time these paw prints would get trampled on or they would count the same print multiple times. So now tiger populations are estimated using something called camera traps. In this method a pair of cameras are set up in a particular area and then they are left there for a few months. Every camera has this infrared beam which is this dotted line that you can see here. So every camera gives out this infrared beam and whenever a tiger crosses this beam and this beam breaks it triggers the cameras to take a shot of the tiger. So this is an actual picture from a camera trap. And this picture helps scientists and experts to study the stripes of the tiger. These stripes. Let's take a closer look at this. So these are the stripes right over here. And these stripes they are as unique as our fingerprints. That's how the scientists can identify the tiger and count all of them in that particular area. But sometimes counting the number of individuals isn't enough to understand the population density of a species. Say you have this garden over here. Over there you have this one huge banyan tree that there's only one of these. And there are multiple about let's say 100 carrot grass plants somewhere over here. Very tiny right over here. This is how they look. Now just because the number of banyan trees is very less compared to the number of the carrot grass plants, we cannot overlook the kind of impact that this huge banyan tree has on the ecosystem there compared to these grass plants. I mean these grass plants are pretty tiny compared to this huge tree right. So in this case a more practical measure would be the biomass of the plants. Which is the mass that is found in living organisms. So instead of measuring the number of trees or plants, we measure their biomass per unit area. And the biomass of this one huge banyan tree is much much higher than the biomass of these tiny carrot grass plants. Now the biomass per unit area that we measured, that's the biomass density of these populations. And the biomass densities, they give us a more accurate idea about the organisms that act on the ecosystem over here. The plant biomass of any area is kind of like a reflection of the various resources that are being used by these plants. Like the solar energy, nutrients and water. So essentially these plants are controlling these resources. So one huge banyan tree, let's write it down somewhere. So a huge banyan tree will use more resources as compared to the smaller carrot grass plants which are going to use much less resources. And as a result of this the impact that this banyan tree will have on the ecosystem will be a whole lot more than the impact of these smaller plants. So that means more biomass density equals more ecological impact. And that's why biomass makes a whole lot more sense in this scenario as compared to the population numbers of these plants. So let's do a quick recap of whatever we have found out so far. Population density talks about the crowdedness of a place. And just because a place has a lot of people doesn't always mean that it's crowded. If in case a place gets too crowded then it ends up affecting the environment in a negative way. Which is why it is essential to keep a measure of population densities of various species. But sometimes measuring the population density through physical counting can become a headache. So we look for indirect approaches. Like counting the paw prints of tigers or measuring the biomass density of a species for better understanding.