Shermin and I have a number of ongoing themes in our discussions. One of them is about sustainable agriculture and how many people can our planet actually support. The latter question has a caveat of course: the answer depends on which technology one would use for growing food. I would surely think that the Earth would support more people if we grew food using conventional (i.e., not sustainable) methods compared to organic. But how much more? Twice as much? Ten times as much?

A recent paper in the journal Nature called "Comparing the yields of organic and conventional agriculture" (free full version available here) by Seufert, Ramankutty and Jonathan Foley (see his TED talk, by the way) offers some insight into the answers. The paper presents the results of a meta-analysis of comparisons of yields between conventional and organic farms. The main result is that organic farms generally have a lower yield, but how much lower depends on the details. For example, vegetables give about 30% lower yield in organic farms than in conventional farms, whereas fruits give pretty much identical yields. Another interesting observation is that, if one compares farms with "best management practices" (not very well defined what this means though) in both types of farms, organic give about 13% less yield than conventional. So, not bad at all!

One interesting likely explanation for the poorer performance of organic systems is that these systems are nitrogen limited whereas conventional systems are not. This means that, when you increase the input of nitrogen into the organic system (e.g., by dumping more fertilizer), its performance goes up. Not the case for a conventional system. The reason why nitrogen is limiting in organic systems is probably because it is released slower from decaying organic matter than is necessary for plant growth.

In short, this article give some clues as to how to optimize food production and gives some hope that organic systems will in the future be able to provide a large fraction of necessary food supply.

Great talk by Andrew Read about the necessity of understanding how evolution works. Feel good about what I am working on :)

Securing natural capital and expanding equity to rescale civilization

I've just read this article by Paul Ehrlich, Peter Kareiva, and Gretchen Daily, published in Nature on 7 June 2012 (link to the original article). The authors clearly operate on a very high level (i.e., not "on the ground"), and therefore the article offers less concreteness than I would have liked. Nevertheless, here is a brief "lazy-man" summary of what I found interesting.

The main premise is: We need to do something soon

It is clear that the human population size and consumption patterns are well above what Earth could support without impairment of vital life-support systems. Population projections suggest that the world will have about 9.5 billion people in 2050 and slightly over 10 billion in 2100.

The authors offer several potential solutions, but only two of them are concrete

1. Make means of contraception accessible in developing countries. One important win–win way to reduce fertility rates is by meeting the ‘unmet need’ for contraception; that is, by supplying safe, modern means to those who do not want a child in the next two years of their lives but are not using any means of birth control. In 53 Asian, African and Latin American countries between 1995 and 2005, an estimated 7–15% of women have an unmet need for contraception. In sub-Saharan Africa, the region where unmet need is greatest, the estimate is about 25% of married women. There are roughly 75 million unintended pregnancies in the world annually and almost half of them end in abortion. Making reproduction education and family planning universally available in the developing world could avert 20 million or more births annually, avoid over 25 million abortions, reduce maternal mortality by 25–40%, and greatly reduce the population growth rate.

2. Educate women. A second win–win way to reduce fertility rates is to raise levels of education, especially of young women. If there were a crash program of education globally, there would be roughly a billion fewer people in 2050 than if there were no effort to keep educational investment commensurate with population size. Although education and subsequent empowerment of women lowers infant and childhood mortality, this effect  is more than offset demographically by the associated growing desire and ability to have fewer children.

Studies of community-based conservation reveal that the more women are involved in local governance, the more effective forest protection and compliance with regulations. This means that women need to be explicitly targeted when designing strategies for promoting conservation and reducing environmental degradation.

I liked the concluding encouragement note

Rapid change has occurred enough times in human history in relation to fundamental aspects of culture to give hope that such change can be triggered now. One need only consider the advances in women’s rights of the past century, the transformation of the racial situation in the United States such that an African American can be elected President, and the collapse of the Soviet Union, to see that cultural change does not necessarily proceed at a glacial pace. And, just as climate change is speeding the flow of glaciers, it should speed the transition of the human enterprise towards a sustainable scale—at which care for all human beings and the natural capital upon which they depend is at the top of the political agenda. The choice seems stark and clear enough: rescaling or global bust.