Air quality
One of the things I noticed recently is that the air quality has substantially improved, compared to the long term average, where I live in Melbourne lately. I suspect that a lot of the pollution in the area I live is caused by internal combustion engine powered transport and now significantly fewer people are travelling at the moment due to the COVID-19 situation. One of the most interesting things is that internal combustion engines don't just pollute the air they are also a significant source of sound pollution. The background noise levels are noticeably lower outside at the moment.
Unfortunately now that the weather is getting a bit colder some of the neighbors here are burning wood for heat. This is particularly terrible for air quality and brings back memories of the haze and smell from the Australian bushfires over the summer of 2019/2020. I feel like if the memories of the bushfires disaster were fresh that people in the city would opt for less polluting forms of heat, but I suspect a lot of people have forgot. I find it remarkable how the bushfires disaster is rarely mentioned now as the public attention has been completely transfixed by the pandemic situation. Only a few months ago the air quality was substantially terrible in many places in Australia due to the smoke haze. The air quality has gone from the worst I've ever experienced in December 2019 and January 2020 to the best I can remember in just a matter of months.
I hope the events surrounding the COVID-19 pandemic give people reason to think about air quality again like they were during and after the bushfires disaster. In many locations in the world air quality hasn't been as good as it is now in years and hopefully this can continue.