Originally conceived to conserve iconic landscapes and wildlife, protected areas are now expected to achieve an increasingly diverse set of conservation, social and economic objectives. The amount of land and sea designated as formally protected has markedly increased over the past century, but there is still a major shortfall in political commitments to enhance the coverage and effectiveness of protected areas. Financial support for protected areas is dwarfed by the benefits that they provide, but these returns depend on effective management. A step change involving increased recognition, funding, planning and enforcement is urgently needed if protected areas are going to fulfil their potential.

The performance and potential of protected areas

The human population is projected to reach 11 billion this century, with the greatest increases in tropical developing nations. This growth, in concert with rising per-capita consumption, will require large increases in food and biofuel production. How will these megatrends affect tropical terrestrial and aquatic ecosystems and biodiversity? We foresee (i) major expansion and intensification of tropical agriculture, especially in Sub-Saharan Africa and South America; (ii) continuing rapid loss and alteration of tropical old-growth forests, woodlands, and semi-arid environments; (iii) a pivotal role for new roadways in determining the spatial extent of agriculture; and (iv) intensified conflicts between food production and nature conservation. Key priorities are to improve technologies and policies that promote more ecologically efficient food production while optimizing the allocation of lands to conservation and agriculture.

Agricultural expansion and its impacts on tropical nature

A focus on novel, confirmatory, and statistically significant results leads to substantial bias in the scientific literature. One type of bias, known as “p-hacking,” occurs when researchers collect or select data or statistical analyses until nonsignificant results become significant. Here, we use text-mining to demonstrate that p-hacking is widespread throughout science. We then illustrate how one can test for p-hacking when performing a meta-analysis and show that, while p-hacking is probably common, its effect seems to be weak relative to the real effect sizes being measured. This result suggests that p-hacking probably does not drastically alter scientific consensuses drawn from meta-analyses.

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The Extent and Consequences of P-Hacking in Science

Tens of thousands of species are threatened with extinction as a result of human activities. Here we explore how the extinction risks of terrestrial mammals and birds might change in the next 50 years. Future population growth and economic development are forecasted to impose unprecedented levels of extinction risk on many more species worldwide, especially the large mammals of tropical Africa, Asia and South America. Yet these threats are not inevitable. Proactive international efforts to increase crop yields, minimize land clearing and habitat fragmentation, and protect natural lands could increase food security in developing nations and preserve much of Earth's remaining biodiversity.

Future threats to biodiversity and pathways to their prevention

The number and extent of roads will expand dramatically this century. Globally, at least 25 million kilometres of new roads are anticipated by 2050; a 60% increase in the total length of roads over that in 2010. Nine-tenths of all road construction is expected to occur in developing nations, including many regions that sustain exceptional biodiversity and vital ecosystem services. Roads penetrating into wilderness or frontier areas are a major proximate driver of habitat loss and fragmentation, wildfires, overhunting and other environmental degradation, often with irreversible impacts on ecosystems. Unfortunately, much road proliferation is chaotic or poorly planned, and the rate of expansion is so great that it often overwhelms the capacity of environmental planners and managers. Here we present a global scheme for prioritizing road building. This large-scale zoning plan seeks to limit the environmental costs of road expansion while maximizing its benefits for human development, by helping to increase agricultural production, which is an urgent priority given that global food demand could double by mid-century. Our analysis identifies areas with high environmental values where future road building should be avoided if possible, areas where strategic road improvements could promote agricultural development with relatively modest environmental costs, and 'conflict areas' where road building could have sizeable benefits for agriculture but with serious environmental damage. Our plan provides a template for proactively zoning and prioritizing roads during the most explosive era of road expansion in human history.

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A global strategy for road building

We agree with Dugdale and colleagues [1] that the continuing underrepresentation of women in the higher echelons of science is both a serious problem and one that merits far more in-depth study than was attempted in our recent analysis [2]. Our unexpected finding that recognized male experts did not profess greater scientific expertise than did female experts with comparable years of experience (failing to support our so-called 'Homer Simpson Effect') was merely an opportunistic observation within a much wider investigation of the long-term fate of tropical nature reserves.

Dugdale et al. suggest that a broader assessment of scientists, especially including younger researchers, might yield different results than those we found. This is plausible but is a much more general question than the one we posed. In taking care not to overgeneralize, we emphasized that our findings applied merely to the sample of researchers we surveyed. We also underscored the fact that our experts were strongly biased in favor of males and concluded that 'the scientific playing field is not yet fully level' [2].

Dugdale et al.'s point about optimal questionnaire design would be taken in a slightly more favorable light had our study been designed to assess gender issues in science. In terms of statistical analysis, the brief format of a TREE Letter (and clear instructions from the journal editor to minimize our statistical treatment, given that TREE does not normally publish original research findings) limited our capacity to provide much quantitative detail. In the ANCOVA that we summarized [2] we did, in fact, conduct the normal safeguards, such as ensuring that our residual-error structure was roughly Gaussian and homoscedastic [3] and that there was no significant gender–expertise interaction; however, it was not possible to squeeze all such ancillary details into our brief Letter.

Although our ANCOVA was quite adequate, we agree with Dugdale et al. that statistical analyses ideally should accommodate the specific distribution of the response variables. In this vein, an ordinal logistic regression [4] provided almost identical results to our ANCOVA [the top-ranked information-theoretic model (AICc weight=0.64) included years of experience only, whereas gender and the gender×years of experience interaction explained almost zero additional deviance]. Overall, the effect size comparing the self-assessment of expertise between males and females was negligibly small (0.012), and slightly favored males.

These statistical details aside, we agree wholeheartedly with Dugdale and colleagues that it is important to investigate why fewer women than men are ascending to the highest ranks of science. If our simple and slightly irreverent Letter [2] should help advance this aim, then we would be delighted.

D. Carolina Useche

Papers

Homing in on the ‘Homer Simpson Effect’: reply to Dugdale et al