No pandemic, plague or epidemic has spread such devastation as the Black Death as far as recorded human history is concerned. Also known as the Great Bubonic Plague or the Pestilence, it resulted in almost 200 million deaths, peaking in Europe from 1347 to 1351. The world population at that time was estimated to be around 500 million and the scourge was believed to have decimated 50-60% of Europe's population.
The plague, caused by Yersinia pestis, was carried by ground rodents (rats), including marmots and is believed to have originated in China 2000 years ago as shown by gene sequencing data (see links below for references). It was terrifying contagious - even clothes brushing against one another could transmit the disease. It was so outrageously quick and deadly - a person who went to bed perfectly healthy (apparently) could be dead the next morning. You can watch the brief video here.
The Black Death was quickly followed by the New World Smallpox Outbreak (56 million deaths); Italian Plague, the Spanish flu, HIV/Aids, Swine flu, SARS, etc. The illustration below will give you a fair idea of all the major pandemics that the world has witnessed in the last 2000 years.
In comparison, the Corona Virus Outbreak or COVID-19 has so far resulted in less than 40,000 deaths worldwide, but it is estimated to have a range of 16 million to 35 million as potential victims by some sources, mainly children and senior citizens, who for some reason seem to lack the immunity that the young adult population has. There are other estimates which place the range between 2 million to 20 million. At this stage, I don't think anyone has a clue. All countries are under a lockdown and only containment seems to be the solution. If it does spread (and not all that many have been tested so far), the mortality rate revised by WHO is now placed around 3.5-4.0%. I am not an expert on this, so shall desist from putting forth any statistics of my own.
What is interesting is the fact that almost all of the previous pandemics resulted in religious, economic and social upheavals in varying degrees across the world, some of them limiting human interactions too, but none so far (as much as I can fathom) resulted in any environmental changes. However, the unprecedented lockdown to this extent in all major as well as minor countries has had far reaching consequences on the environment.
The World Economic Forum has published satellite images of the (positive) environmental impact of COVID-19 - it is really something that each person needs to be aware of. However, whether there would be a sustained lasting impact on the environment is difficult to conjecture. I am not saying that this pandemic is a good thing - it is scary and human lives are at stake - however, I am saying that as we become cognizant of how much we influence the environment adversely, we should learn from this and global leaders should listen to Greta Thunberg and take immediate steps to minimize our carbon footprint.
Here are a few things that have dramatically changed in the last month or so -
Significant improvement in air quality (far lower air pollution).
Nitrogen dioxide emissions, which are closely linked to factory output and vehicles on the roads, has gone down drastically.
Steep drop in CO2 emissions across various countries.
Clearer water, especially where water transport systems have come to a grinding halt.
Slowing down economic activity, shutting down offices, schools, colleges and factories has also resulted in significantly reducing all greenhouse gas emissions.
As people stay locked in at home, or in self-quarantine, there is lesser food waste and also a significant reduction in the daily urban waste generation by way of plastics, disposables, packaging material, takeaway containers, etc. However, the medical waste has gone up.
The noise pollution levels have also gone down significantly, notably in countries with large population - there are no public events, no vehicles on the roads, no honking, no public transport.
Airline emissions have gone down, although this has resulted at the airline industry staring at bankruptcy if they are not bailed out or suitable economic measures are not undertaken.
Emissions from coal combustion are also falling across the world.
Commercial use of energy has fallen rapidly, even as domestic consumption has gone up. However, it appears that the fall is far higher than the corresponding increase in domestic use.
Particulate matter levels have dropped significantly.
Human beings are spending more time at home with their families than they ever did before.
Nature is sending us a message. For all those who did not believe in Global Warming or the disastrous effects of human economic activity, the message is loud and clear. If a couple of weeks can lead to such dramatic changes, imagine the quality of human life if this were to be made permanent. NOT by another virus or by Gaia's revenge, but merely by global leaders waking up to the (now) established facts and taking urgent steps to reverse the damage that has been done to this beautiful planet over the past few hundred years.
References:
https://www.history.com/topics/middle-ages/black-death
https://en.wikipedia.org/wiki/Black_Death
https://www.visualcapitalist.com/history-of-pandemics-deadliest/
https://www.weforum.org/agenda/2020/03/emissions-impact-coronavirus-lockdowns-satellites/