Our little island of Ireland is home to a wonderful range of biodiversity. We have listed below all the species found across the country arranged by taxonomic group, starting with the largest first. You might be surprised to see the more familiar species at the end of the list. These numbers were compiled by Ireland's excellent National Biodiversity Data Centre, based in Co. Waterford:

Insects

11,422
​All our creepy-crawlies without a backbone, supported by exoskeletons and with six legs, with or without wings; from bees to butterflies, beetles to dragonflies.
(Photograph: National Biodiversity Data Centre)

NON-INSECT INVERTEBRATES

8,000
Like insects, they don't have a back-bone. Unlike insects, they don't need to have six legs; from millipedes to mussels, spiders to lobsters. ​

Fungi

5,500
​The familiar decomposers, examples include mushrooms and molds.

Vascular Plants

2,328
​These are like advanced plants. They have a vascular system used to transport water, minerals and photosynthesis products around the plant; examples include flowers and trees.

Lichens

1,134
​Lichens are the byproduct of when an algae and fungi merge to form a new organism. Seen all over rocks and trees, can be crusty or leafy and feel dry and brittle.
(Photograph: National Biodiversity Data Centre)

Algae

1,079
Like very simple plants. They do not have a vascular system but they do photosynthesize. Usually found in water. Examples include seaweeds.
(Photograph: National Biodiversity Data Centre)

Bryophytes

797
​Like very simple plants. They do not have a vascular system but they do photosynthesize. They are more structurally advanced than algae. Usually found on land. Examples include mosses.
(Photograph: National Biodiversity Data Centre)

Fish

592
​Including marine fish and freshwater fish. 

Birds

457
Our warm-blooded, feathered friends with beaks and wings.
(Photograph: Padraig Whooley, IWDG)

Marine Mammals

26
Mammals are warm-blooded, have hair, give birth to live young and feed them on milk. Our marine mammals are those found in our rivers and seas.

Land Mammals

25
The same mammalian features as above, but they spend their time living on dry land.
 (Photograph: Paul van Hoof)

Air Mammals

9
Bats! Just like any other mammal, but they can fly... pretty cool! Bats are the only mammals in the world that are capable of powered flight.

AmphIBians & Reptiles

6
Amphibians spend time both on land and in water during development while reptiles are covered in scales. Both are cold blooded. We only have one reptile in Ireland, the common lizard.
References
National Biodiversity Data Centre - Taxonomic Groups​