I have a world that has unexpected lifeforms detected. There are to-be-revealed reasons for it, but the way the ecosystem is set up is:
- Microbial life is abundant everywhere
- There is a single species of plant form that has colonized the land
- There is a single avian species that feeds on those plants
The rest of the life exists in the oceans, in which significant biodiversity exists. I am willing to change things slightly so that, for example, near the shorelines there is more land-based biodiversity if the planet itself seems completely unrealistic.
What would the consequences be of such an ecosystem? At the very least it would be extremely susceptible to microbial disease, since it's basically a planet-wide monoculture. What rules would have to exist on that life to work? I can imagine that the life should only exist at a certain latitude range, but is there anything else?