Boldness and conformity among conservation biologists

Should conservation targets, such as the proportion of a region to be placed in protected areas, be socially acceptable from the start? Or should they be based unapologetically on the best available science and expert opinion, then address issues of practicality later?

Reed Noss and coauthors pose this dilemma in Bolder thinking for conservation (published in Conservation Biology), advocate the second approach and accuse other conservation biologists of timidity, anthropocentric bias and giving in to the global economic agenda. But then they fall back to an - exactly - middle of the ground position. 

Their goal is to "maintain the full breadth of biodiversity - the variety of genes, species, and ecosystems that constitute life on Earth." This entails "maintaining viable populations of native species, representing ecosystems across their range of variation, and promoting resilience of ecosystems to environmental change." They claim that current conservation targets will not meet this goal: 

Targets for 2020 set at the Nagoya Conference include protected areas covering 17% of terrestrial areas and inland waters, 10% of marine and coastal areas, and restoration of at least 15% of degraded ecosystems. These targets are woefully below what the results of most scientific studies show are necessary [...]

Such scientific studies estimate how much area is needed, for example, to represent all species at least once or to guarantee a low extinction probability of threatened species. Noss and coauthors advocate "50% terrestrial area managed with conservation of nature as a primary objective — slightly above the mid-point of recent evidence-based estimates — as a scientifically defensible global target." 

[C]onservation professionals must become part of the constituency that promotes life on Earth. Our task is not to be beaten down by political reality, but to help change it. Nature needs at least 50%, and it is time we said so.

However, maintaining the current full breadth of biodiversity requires protecting 100% of the Earth, not "at least 50%." It is time someone says so. Noss and coauthors are probably aware of this but perhaps they are conformist or anthropocentric.

Not that I advocate protecting 100% of the Earth. I do have an anthropocentric "bias".