Protected areas, biodiversity loss, jobs and human population growth

After convincingly arguing that current conservation efforts, including protected areas, cannot stop biodiversity losses, Camilo Mora and Peter F. Sale call for "stabilizing the size of the world’s human population" (Ongoing global biodiversity loss and the need to move beyond protected areas: a review of the technical and practical shortcomings of protected areas on land and sea, Marine Ecology Progress Series).

One could safely argue that biodiversity threats are ultimately determined by the size of the world’s human population and its consumption of natural resources. The explosive growth in the world’s human population in the last century has led to an increasing demand on the Earth’s ecological resources and a rapid decline in biodiversity.

They add that conserving biodiversity is not their only reason for "targeting human population growth directly."

[H]uman population growth may also lead to economic (e.g. high competition for and/or shortages of jobs; Becker et al. 1999) and societal (e.g. shortages of food and water, lack of universal primary education, increase in communicable disease, etc.; Campbell et al. 2007) problems [...]

I have checked the papers by Becker et al. and Campbell et al. In their op-ed, Campbell et al. 2007 do not relate the lack of universal primary education to population growth but to family size and do not relate communicable disease to population growth but mention that "preventing unintended pregnancies is the most cost-effective way of reducing mother-to-child transmission of AIDS." Campbell et al. do not mention water but do imply that hunger is related to population growth - ignoring the fact that hunger has been decreasing as population has increased.

Becker et al. 1999 do not mention job shortages or job competition. And, contrary to what Mora and Sale's citation implies, they are quite optimistic about productivity and human capital improvements in a growing population. This is Becker et al.'s conclusion:

Population may reduce productivity because of traditional diminishing returns from more intensive use of land and other natural resources. However, larger populations encourage greater specialization and increased investments in knowledge, mediated in part through bigger and more important cities. Therefore, the net relation between greater population and per capita incomes depends on whether the inducements to human capital and expansion of knowledge are stronger than diminishing returns to natural resources.

The  potential  importance of increasing returns to population in a world with rapidly growing population justifies a reconsideration of the relation between population and per capita incomes. 

Fortunately, this is what we are witnessing - a growing human population that is getting more productive and wealthy.