All species are important! Indeed, there have been multiple occasions where humans have tried to recreate ecosystems and missed some minor member -leading to the collapse of the ecosystem. There are many easily overlooked species which we might miss if we were to try to recreate.
The whole ecosystem is essential, from the largest elephant to the smallest insect.
Never-the-less, in recent years a new term has become increasingly important “umbrella species”. These species are (for one reason or another) such that if they are protected then many others will also be saved.
One example is Elephant. If you have a large enough reserve for an elephant population to survive and thrive, then it is also going to be big enough for many others. However, if you loose the last of your elephants the reserve may shrink, or the number of visitors may fall. Either is likely to spell a decline of the wilderness that was once there.
This list may well get added to over time. There is for instance no sea creatures among this list, and nothing from Australia. Still over time I will create a page for each, and I hope long-term for each to link to places you can go and see them, as well as articles that have been covered on the subject in this blog. I am also keen to keep a closer eye on sub species, as well as specific populations, which will I hope be covered over time on each page.