Bob davison describes the endangered species act (esa) as an effective tool for conserving biological diversity. what is his rationale for the value of focusing on individual species? bob davison describes the endangered species act (esa) as an effective tool for conserving biological diversity. what is his rationale for the value of focusing on individual species? a focus on individual species is cheaper than protecting entire ecosystems. establishing public empathy for charismatic species provides an opportunity to educate people about lesser-known species. the public is not concerned about the economic costs of individual species recovery. the public tends to value intact ecosystems over particular plant and animal species.