Final answer:
The author's position on swimming with manatees is developed through references to Marsh's view on human impact on biodiversity and Mascia and Claus's property rights approach in conservation, suggesting that human activities, such as swimming with manatees, can disrupt these creatures' natural habitat and behaviors.
Step-by-step explanation:
In "Excerpt from Saving Manatees," the author develops his position about people swimming with manatees by highlighting the potential negative impacts of human interactions on these aquatic mammals. One significant detail provided is the reference to George Perkins Marsh's idea that humans can act as a 'new geographical force' with considerable impact on biodiversity. In this context, the concern is that swimming with manatees can disrupt their natural behaviors and well-being.
The second detail involves the insights from the Conservation Biology article by Mascia and Claus which suggests a property rights approach to understanding human displacement from protected areas, including those inhabited by manatees. This supports the author's position by implying that manatees have a right to their habitat without human interference.