I want to know the answer to the following question:
What is probably the reason there are so many unique plants in Karoo?
All the background I'm provided with is that "One of these, known as the Succulent Karoo, is home to over 5,000 species of plants, nearly half of them endemic; Approximately 10 percent of the world's succulents are found in the Karoo.". Is that enough to answer the question?