Leeches Measuring Biodiversity

In a recent study, Harvard researchers took blood samples of leeches' meals to measure which animals are present in the Ailaoshan National Nature Reserve in Yunnan, China. Within three months, the researchers collected more than 30,000 leeches to extract DNA to evaluate the population of 80 species, including amphibians, mammals, birds, and squamates. This new method of using leeches is a cheaper and simpler biodiversity surveillance instrument.

After reading about this research project, I found it interesting how they were able to conclude that their data was accurate and to scale. I can understand that they can identify all of the species using DNA from multiple sources of leeches and that there can be a denser amount of one species, but the one question that popped into my head: Can this method help calculate how many of one species is there in a region?

The scale is just the ratio of one species compared to others, but that doesn't determine that actual number. For example, the ratio of pandas to platypuses can be 1:2, but there is only 25 pandas, making there to be 50 platypuses. These numbers would be considered as scarce, and I'm not sure leeches will be able to measure which animals are close to extinction.

Siliezar, Juan. “Using Leeches to Map Biodiversity.”, Harvard Gazette., https://news.harvard.edu/gazette/story/2022/06/using-leeches-to-map-biodiversity/.