For over seven hundred million years, dinosaurs ruled the earth. Some had huge teeth that ripped the flesh of their target. However, there were also some plant eating dinosaurs too that could graze from the top of the trees. The dinosaurs’ dominant position was undoubtedly assured to last long but, about 65 million years ago, the dinosaurs disappeared. Perhaps a comet hit the earth and created a great dust and the sun’s light and heat couldn’t reach the earth for a long time or the earth’s climate changed due to some other reason which made the planet inhospitable. This was not only for dinosaurs but also for thousands of other species of plants and animals. Today, there are so many plants and species that are becoming extinct way faster than the dinosaurs disappeared. The earth is facing an great threat to its biodiversity, the diversity of all the living things that inhabit the oceans and continents. The threat is unprecedented because it doesn’t come from a comet headed to earth for another disastrous event. The threat comes from the rise of a single species that has given its hundred percent in putting the other species at risk and that species is the human species. The sum of all living species in biosphere is called biodiversity and the factors like habitat destruction, hunting, poaching, pollution, introducing foreign species, the green house effect etc. are causing a great threat to it. We are living in a period of mass extinction. Everyday, the species are becoming extinct and the whole food web is affected by this. The human actions are pushing nature to its limits. Here are some of the major causes of biodiversity loss.
1. Exploitation by Humans
It is pretty clear that human population and great resource utilization affects not just our social and economical well being but also our biodiversity. It translates into decrease in species richness because no two things can occupy the same place at the same time. If human is living in a given place, fewer native plants and animals can live there. Another human mediated cause of biodiversity loss is land use changes. It includes things like habitat destruction and conversion of natural habitat to human use that isn’t necessarily compatible with the organisms that are native there. This includes crop monoculture that results in a very dramatic drop in species richness in a given habitat. When people think about habitat destruction and conversion, they think about slash and burn agriculture or destroying rainforests or removing the tops of mountains to get the resources like coal but there are ocean use changes too that we can not ignore. The degradation of the local habitats through human activities like the leaching of harmful chemicals from mines into the water table causes downstream effects. Waterborne pollutants can pop out in very unusual places. There are also dead zones in the oceans caused by nitrogen fertilizers that wash into rivers. When the rivers flow into the sea, the nitrogen causes blooms of bacteria which in turn use up the oxygen. Anything that tries to be active in an area where the oxygen has been used up by the bacteria, is not going to last very long. Resource exploitation like hunting, cutting trees, destroying forests, overfishing, mining and urbanization is another human mediated cause of biodiversity loss.
2. Introduced Species
In the first glance, it might seem that introducing new species might be good for biodiversity but let us face it. The term introduced species is synonymous with exotic species. It is the opposite of a native species which is one that occurs in an area unnaturally without human intervention. When we introduce a species to a new area, anything that is living on, in or with that species, comes along with it. For example, if you bring a cow from one place and move it to another, it is going to bring along all the parasites that that cow normally deals with. However, some introduced species can provide new food sources and habitats for native species but most of the times, the introduced species certainly go beyond just living peacefully alongside the natives as they have competitive advantages. They lack natural controls such as predators or diseases that keep them in check in their native habitats. Another good example of invasives are pathogens which include disease causing organisms like fungi or bacteria or even viruses.
3. Climate Change
Everything we do locally has global consequences. Increases in the amount of carbon dioxide in the atmosphere mostly come from the burning of fossil fuels. Fossil fuels contain huge amounts of carbon and when they are burned, they not only release heat energy, but they also release carbon dioxide. That is why atmospheric CO2 is increasing and causing the change in climate. Other factors like greenhouse effect are also playing a great role in biodiversity loss through climate change. The current rate at which CO2 content is changing, is the running theme behind all the problems with climate we are seeing today. According the the most conservative IPCC estimates, the global temperature on earth is going to rise 1.1 to 2.9 degrees Celsius during this century when the melting glaciers is another great global issue already. Many habitats and the species living in them are destroyed because of natural calamities like hurricanes, floods and volcanoes.
4. Ocean Acidification
Thirty to forty percent of big clouds of CO2, which is produced by human activity, end up dissolved in the ocean and the rest stays in the atmosphere. This huge amount of CO2 that gets dissolved in the oceans is definitely going to increase the level of acid in them. Another big reason of ocean acidification is great oil spills in the oceans. Over the past 35 years, more than 997 million gallons of oil has been split in the worst oil disasters of human history. The effect on marine life has been quite devastating. Acid rain is also a result of ocean acidification. It also cause negative effects on variety of marine species and plants and the marine food chain is also going to be very badly affected.