Second

Each species of flora continuously required many chemical compounds.

Each chemical compound had a cycle to sustain its availability.

Each cycle required many other species.

Thus, each species of flora was indirectly dependent on many other species to keep the chemical cycles going, to keep it alive.

"The same must be true for you," Rui sharply deduced. "In fact, I cannot imagine how many chemical cycles you depend on. Millions? Probably billions with just how enormous and magical your existence is."

That next deduction followed smoothly.

"If you require billions of chemical cycles to sustain your existence, and assuming that each chemical cycle requires several species to sustain it, then essentially you require many billions of species to survive in order to sustain your life."