According to scholars, there weren't 15,000 since that number is arrived at by trying to translate 'kind' into 'species'. The actual count of animals is less than 300 total. Leviticus and Deuteronomy list those animals deemed 'clean' and 'unclean' and those lists combined total about 30 animals.
The only ones trying to state that there was an extremely large amount of animals are Creationists who don't believe evolution to be a viable theory, and atheists who like to criticize everything in the Bible without bothering to research what it contains.
Both are missing the point of the narrative.
Define "kind"