Carbon opportunity cost increases carbon footprint advantage of grain-finished beef.

Beef production accounts for the largest share of global livestock greenhouse gas emissions and is an important target for climate mitigation efforts. Most life-cycle assessments comparing the carbon footprint of beef production systems have been limited to production emissions. None also consider potential carbon sequestration due to grazing and alternate uses of land used for production.

Land-use intensity of electricity production and tomorrow's energy landscape.

The global energy system has a relatively small land footprint at present, comprising just 0.4% of ice-free land. This pales in comparison to agricultural land use- 30-38% of ice-free land-yet future low-carbon energy systems that shift to more extensive technologies could dramatically alter landscapes around the globe.

Forecasting future global food demand: A systematic review and meta-analysis of model complexity.

Predicting future food demand is a critical step for formulating the agricultural, economic and conservation policies required to feed over 9 billion people by 2050 while doing minimal harm to the environment. However, published future food demand estimates range substantially, making it difficult to determine optimal policies. Here we present a systematic review of the food demand literature-including a meta-analysis of papers reporting average global food demand predictions-and test the effect of model complexity on predictions.

Reducing the environmental impact of global diets.

It is well established in the literature that reducing the amount of meat in global diets would reduce the environmental impacts of food production. However, changes to livestock production systems also have significant potential to reduce environmental impacts from meat production, and yet are not as widely discussed in the literature. Modern, intensive livestock systems, especially for beef, offer substantially lower land requirements and greenhouse gas emissions per kilogram of meat than traditional, extensive ones.

The ecological footprint remains a misleading metric of global sustainability.

In this Formal Comment, Blomqvist et al. note that the main points of their Perspective, “Does the Shoe Fit? Real versus Imagined Ecological Footprints,” are robust to Rees and Wackernagel's response, “The Shoe Fits, but the Footprint is Larger than Earth.”

Does the shoe fit? Real versus imagined ecological footprints.

The global overshoot indicated by Ecological Footprint calculations consists entirely of an unreliable reframing of human carbon emissions and none of the five other land-use categories—cropland, grazing land, built-up land, fishing grounds, and forests. The Ecological Footprint is therefore “so misleading as to preclude its use in any serious science or policy context,” argue Blomqvist et al. in this perspective.

Does the terrestrial biosphere have planetary tipping points?

Tipping points--where systems shift radically and potentially irreversibly into a different state--have received considerable attention in ecology. Although there is convincing evidence that human drivers can cause regime shifts at local and regional scales, the increasingly invoked concept of planetary scale tipping points in the terrestrial biosphere remains unconfirmed. By evaluating potential mechanisms and drivers, we conclude that spatial heterogeneity in drivers and responses, and lack of strong continental interconnectivity, probably induce relatively smooth changes at the global scale, without an expectation of marked tipping patterns.