The main reason the ecosystem is how it is today is because all of the adaptations between the organism to successfully make an ecosystem.
If the plants did not grow low to the ground, then the animals would have no food source or primary consumer so the ecosystem would die off ad there would be no populations.
The Tundra biome is in secondary succession because of al the natural disasters and pollution caused by all the human impacts.
One of them being the history of the oil spills and drilling for oil which containment and release harmful gases in the air which forces species to migrate and move to a safer environment.
The evidence used to support the secondary succession is the amount of species that is left over like the decreasing amount of fish and penguins left in the ocean because of the all of the oil spills etc.
This can lead to the entire biome banishing because of all the pollution, majority of the food source is gone meaning populations will being to starve and decrease until there in none left this is why it is important to take care of the environment.
