Here's why:

* Hardy and adaptable: Lichens can survive in harsh conditions with little soil, water, and nutrients. They can even break down rock to create a thin layer of soil.

* Nitrogen fixation: Some lichens can fix nitrogen from the atmosphere, making it available for other plants.

* Pioneer role: Lichens are often the first organisms to colonize bare rock, creating a foundation for other plants to grow.

Other common pioneer organisms include:

* Mosses: Similar to lichens, they can tolerate harsh conditions and help create a thin layer of soil.

* Grasses: These can grow in thin soil and can tolerate some disturbance.

* Certain bacteria and fungi: These can break down organic matter and create nutrients for other organisms.

Succession is the process of change in the species structure of an ecological community over time. Pioneer organisms play a crucial role in initiating this process, paving the way for more complex communities to develop.