Zia Mehrabi

Trends in Global Agricultural Land Use: Implications for Environmental Health and Food Security

The eighteenth-century Malthusian prediction of population growth outstripping food production has not yet come to bear. Unprecedented agricultural land expansions since 1700, and technological innovations that began in the 1930s, have enabled more calorie production per capita than was ever available before in history. This remarkable success, however, has come at a great cost. Agriculture is a major cause of global environmental degradation. Malnutrition persists among large sections of the population, and a new epidemic of obesity is on the rise. We review both the successes and failures of the global food system, addressing ongoing debates on pathways to environmental health and food security. To deal with these challenges, a new coordinated research program blending modern breeding with agro-ecological methods is needed. We call on plant biologists to lead this effort and help steer humanity toward a safe operating space for agriculture.

Plant–Soil Feedback: Bridging Natural and Agricultural Sciences

In agricultural and natural systems researchers have demonstrated large effects of plant-soil feedback (PSF) on plant growth. However, the concepts and approaches used in these two types of systems have developed, for the most part, independently. Here, we present a conceptual framework that integrates knowledge and approaches from these two contrasting systems. We use this integrated framework to demonstrate (i) how knowledge from complex natural systems can be used to increase agricultural resource-use efficiency and productivity and (ii) how research in agricultural systems can be used to test hypotheses and approaches developed in natural systems. Using this framework, we discuss avenues for new research toward an ecologically sustainable and climate-smart future.

The Conventional Versus Alternative Agricultural Divide: A Response to Garibaldi et al.

Garibaldi et al. [1] provide a much-needed discussion on the state of our knowledge on the socioecological impacts of different farming choices. They highlight a lack of data on comparisons of different farming choices, and recommend a research program for comparing alternative versus conventional systems as a way to solve this problem. We discuss here some of the ongoing challenges the scientific community faces in making conventional and alternative system comparisons. Although we see value in categorizing farming systems, we contend that our classifications are never black and white in their outcomes – there can be environmentally sound and socially just conventional systems, and alternative systems that are environmentally and socially detrimental.

The challenge of feeding the world while conserving half the planet

Amid widespread concerns about biodiversity loss, a single clear conservation message is engaging leading conservationists: the proposal to give half the surface of the Earth back to nature. Depending on the landscape conservation strategy, we find that, globally, 15–31% of cropland, 10–45% of pasture land, 23–25% of non-food calories and 3–29% of food calories from crops could be lost if half of Earth’s terrestrial ecoregions were given back to nature.In response to continuing habitat and biodiversity loss, leading conservationists have proposed setting aside half the earth for nature. This study evaluates the trade-offs with food production and finds losses in croplands, pasture and calories that vary with the conservation strategy.

Does no-till agriculture limit crop yields?

No-till is an agricultural practice widely promoted by governments, development agencies, and agricultural organisations worldwide. However, the costs and benefits to farmers adopting no-till are hotly debated 1–4. Using a meta-analysis of unprecedented study size, Pittelkow et al.5 reported that adopting no-till results in average yield losses of -5.7%, but that these losses can be limited with the added implementation of two additional conservation agriculture practices - crop rotation and crop residue retention, and in dry environments. They claimed that, as a result, resource limited smallholder farmers, that are unable to implement the whole suite of conservation agriculture practices are likely to experience yield losses under no-till. In a re-evaluation of their analysis, we found that they overly biased their results toward showing that no-till negatively impacts yields, and overlooked the practical significance of their findings. Strikingly, we find that all of the variables they used in their analysis (e.g. crop residue management, rotation, site aridity and study duration) are not much better than random for explaining the effect of no-till on crop yields. Our results suggest that their meta-analysis cannot be used as the basis for evidence-based decision-making in the agricultural community.

The cost of heat waves and droughts for global crop production

Heat waves and droughts are a key risk to global crop production and quantifying the extent of this risk is essential for insurance assessment and disaster risk reduction. Here we estimate the cumulative production losses of six major commodity groups under both extreme heat and drought events, across 131 countries, over the time period of 1961-2014. Our results show substantial variation in national disaster risks that have hitherto gone unrecognised in regional and global average estimates. The most severe losses are represented by cereal losses in Angola (4.1%), Botswana (5.7%), USA (4.4%) and Australia (4.4%), oilcrop losses in Paraguay (5.5%), pulse losses in Angola (4.7%) and Nigeria (4.8%), and root and tuber losses in Thailand (3.2%). In monetary terms we estimate the global production loss over this period to be

On the synchronized failure of global crop production

237 billion US Dollars (2004-2006 baseline). The nations that incurred the largest financial hits were the USA (

An open-access dataset of crop production by farm size from agricultural censuses and surveys

116 billion), the former Soviet Union (

How much of the world's food do smallholders produce?

37 billion), India (

Current and Potential Contributions of Organic Agriculture to Diversification of the Food Production System

28 billion), China (