Siberian Glowcaves

Siberia is one of the hardest hit areas during the holocene extinction. The amount of CO2 in the air from constant mining has left the once lush taiga into a wasteland. Once the Calidocene rolls around and the area recovers, the plains of ash give way to wetlands, savannas, and deciduous forests.

However a brand new biome goes unnoticed underground. Acid rain and sinkholes caused by fracking and other mining operations leave a vast cave system going throughout the entirety of North Asia.

Fungi that dissolve rock are quick to colonize these cave systems and invertebrates soon follow to eat the fungi and lichens growing inside. This gives a perfect opportunity for non-photosynthetic plants like parasitic and carnivorous plants to establish to food-rich community underground. To consume the plants, fungi, and invertebrates underground, land vertebrates move underground. 

When insects and other animals enter the caves, the fungi develop bioluminescence to help spread their spores around, the animals are drawn to the light and accidentally carry spores around.

Fungi aren't the only ones to develop bioluminescence though, the invertebrates in the cave systems have developed bioluminscence to identify each other and to light up their surroundings.

These bioluminscent adaptations allow for these gigantic cave systems to become artificially lit up. It also helps it become a paradise for flora and fauna.