Answer:
By overpopulation.
Step-by-step explanation:
The easiest way for an ecosystem to be destroyed naturally is through overpopulation. This is when a species(typically invasive) overtakes the area. Thus resulting in not enough food for the other organisms, further leading to their migration away from the area or death(due to failure to thrive and lack of resources). Hope this made sense and let me know if you want a further explanation. :)