Pan-species listing is not a term that many people are familiar with. Yet, variants of the hobby have been with us for a while. On one hand that is because this term has not been widely founded. In fact, the most mainstream use of this term is by an English site where pan-species listers document their lists, and consequently by the same site's facebook page. Most other examples of the term exist in blogs, from Dr. Denton's blog to the mostly decommissioned page by Mark Telfer.
Listing is a popular hobby for many people. Birdwatchers are the most well-known hobbyists that keep lists. Less well known are others with interests in botany or butterflies which keep their own list. But few are insane enough to try and tackle not only birds and butterflies but also plants, fungi, mammals, and, shudder, algae and grasses.
Pan-species listing at present is defined by the process of recording every taxon that you as a person have personally seen in the wild. Everything from that magpie to the dandelion you just squashed with your foot count on a pan-species list! You might be thinking, "well plants and birds and butterflies are cool, but ew spiders and ugh algae". The great news is that there is no requirement to actually record everything. This is your personal hobby and you can ignore all the spiders you want!
Pan-species listing is great because it really opens you up to the natural world. I used to be quite disappointed with a certain concrete neighbourhood of mine, until I started paying attention to the weeds in the sidewalk and the smaller denizens of the hedgerows. In a couple of years I had amounted over 450 species, in what may have been the most boring habitat on the planet. That was a really eye-opening experience for me to think that I had seen more species in a dry urban neighborhood than I have seen birds in the world.
One of the coolest part of listing is recognizing not only the species you used to walk past or step on, but the boundary between habitats and ecosystems based on the presence or absence of one species or another. That's when you start appreciating nature for what it really is, besides large conspicuous and colourful organisms. You soon start perceiving things very differently!
I think it is something everyone should think about. The hobby has encouraged me to get outside far more regularly than I would otherwise. Despite the time it takes me to sort photos at the end of the day I am more than thankful for an introduction to this hobby. Some people keep not only a global list, but a garden list for everything they've seen in their garden. Some people keep county lists, or country lists. The possibilities are endless.
Of course, this is not the only hobby you can get involved in if you want to get outside and appreciate nature. You don't even have to keep a list to enjoy the outdoors.
Each person has their own personal preferences. For instance, some people count shells on the beach. Other people count galls, Others, like me, don't count shells (my argument being they are not the real living organism), and others ignore galls (the argument being you are not really seeing the actual organism inside, just evidence of its presence). Generally the universal rules are:
-no captive organisms (with rare exceptions varying according to person; for instance if someone phoned me up and said they found a clifdon nonpareil in Hampshire, and then caught it an a box and drove it over to me, I'd count that!). So this means no zoo creatures, no garden plants, and no pet daschunds!
-living organisms only (if its long dead, it doesn't count. I may be guilty of counting some recently dead species, but only within hours. The specifics vary from person to person.).
-have fun! Please do, that's the whole point.
How do I start?
How you start is up to you! But I recommend a site such as iNaturalist.org. These sites not only automatically keep track of your list for you but your sightings contribute to global data sites, and plus you can get community input on your ID if you are not sure! If your site has an app where you can just take out your iPhone and take down records out in the field (such as iNaturalist), then even better! I generally prefer to just freely hike, take photographs, and make my sightings at the end of the day though.
As for learning the species the best tactic for me was always to read through a field guide a few times. Then I would go out into the field and try and put my knowledge to the test. The best learning experience for me was photographing something I didn't know, then running it through the field guide, and then having it confirmed or corrected by an expert. Not only do you learn why your species is or isn't what you thought it was, but you will find insight on how to make these IDs more efficient. Insects for instance benefit from a photo that shows the bug straight. Trying to ID from obscure angles is tough!
But here is my biggest tip. Learn the families! This applies to almost every group, whether its an insect, bird, plant, or moss. Recognizing the family cuts 80% of the initial work. It can be ridiculously time consuming trying to identify a flower if you don't even know what family it might be. You can quickly rule out several thousands of species that way. Almost all families end in -dae ("dee"), except plants and fungi which end in "-aceae ("ay-see-ee").
Most importantly, have fun! It is your personal hobby and you can invest as much or as little as you want into it.
Now get out there and start watching nature!