A nice 2008 PNAS paper Maps of random walks on complex networks reveal community structure (PNAS 105, 1118) [pdf] by Martin Rosvall and Carl T Bergstrom creates beautiful and informative visualizations of citation networks in science (from 2004 ISI data) using a neat method for visualizing and analyzing complex networks. Martin Rosvall has a created a website that enables the creation of similar maps of network data.
Tag Archives: PNAS
1)The Economist writes about the success of large scale Brazil agriculture in Brazilian agriculture: The miracle of the cerrado. The article concludes:
The bigger question for them is: can the miracle of the cerrado be exported, especially to Africa, where the good intentions of outsiders have so often shrivelled and died?
There are several reasons to think it can. Brazilian land is like Africa’s: tropical and nutrient-poor. The big difference is that the cerrado gets a decent amount of rain and most of Africa’s savannah does not (the exception is the swathe of southern Africa between Angola and Mozambique).
Brazil imported some of its raw material from other tropical countries in the first place. Brachiaria grass came from Africa. The zebu that formed the basis of Brazil’s nelore cattle herd came from India. In both cases Embrapa’s know-how improved them dramatically. Could they be taken back and improved again? Embrapa has started to do that, though it is early days and so far it is unclear whether the technology retransfer will work.
A third reason for hope is that Embrapa has expertise which others in Africa simply do not have. It has research stations for cassava and sorghum, which are African staples. It also has experience not just in the cerrado but in more arid regions (called the sertão), in jungles and in the vast wetlands on the border with Paraguay and Bolivia. Africa also needs to make better use of similar lands. “Scientifically, it is not difficult to transfer the technology,” reckons Dr Crestana. And the technology transfer is happening at a time when African economies are starting to grow and massive Chinese aid is starting to improve the continent’s famously dire transport system.
Still, a word of caution is in order. Brazil’s agricultural miracle did not happen through a simple technological fix. No magic bullet accounts for it—not even the tropical soyabean, which comes closest. Rather, Embrapa’s was a “system approach”, as its scientists call it: all the interventions worked together. Improving the soil and the new tropical soyabeans were both needed for farming the cerrado; the two together also made possible the changes in farm techniques which have boosted yields further.
Systems are much harder to export than a simple fix. “We went to the US and brought back the whole package [of cutting-edge agriculture in the 1970s],” says Dr Crestana. “That didn’t work and it took us 30 years to create our own. Perhaps Africans will come to Brazil and take back the package from us. Africa is changing. Perhaps it won’t take them so long. We’ll see.” If we see anything like what happened in Brazil itself, feeding the world in 2050 will not look like the uphill struggle it appears to be now.
2) On the Agricultural Biodiversity Weblog Luigi responds to the Economist article, in a post Is there really no downside to Brazil’s agricultural miracle?. He praises their coverage of agriculture, but lambasting their blindness to the consideration of social and ecological costs. He writes:
It points out that the astonishing increase in crop and meat production in Brazil in the past ten to fifteen year — and it is astonishing, more that 300% by value — has come about due to an expansion in the amount of land under the plow, sure, but much more so due to an increase in productivity. It rightly heaps praise on Embrapa, Brazil’s agricultural research corporation, for devising a system that has made the cerrado, Brazil’s hitherto agronomically intractable savannah, so productive. It highlights the fact that a key part of that system is improved germplasm — of Brachiaria, soybean, zebu cattle — originally from other parts of the world, incidentally helping make the case for international interdependence in genetic resources.1 And much more.
What it resolutely does not do is give any sense of the cost of all this. … I was really thinking of environmental and social costs. The Economist article says that Brazil is “often accused of levelling the rainforest to create its farms, but hardly any of this new land lies in Amazonia; most is cerrado.” So that’s all right then. No problem at all if 50% of one of the world’s biodiversity hotspots has been destroyed.2 After all, it’s not the Amazon. A truly comprehensive overview of Brazil’s undoubted agricultural successes would surely cast at least a cursory look at the downside, if only to say that it’s all been worth it.
3) Holly Gibbs and colleagues have a new paper in PNAS – Tropical forests were the primary sources of new agricultural land in the 1980s and 1990s (doi/10.1073/pnas.0910275107). They write:
This study confirms that rainforests were the primary source for new agricultural land throughout the tropics during the 1980s and 1990s. More than 80% of new agricultural land came from intact and disturbed forests. Although differences occur across the tropical forest belt, the basic pattern is the same: The majority of the land for agricultural and tree plantation expansion comes from forests, woodlands, and savannas, not from previously cleared lands.
Worldwide demand for agricultural products is expected to increase by ~50% by 2050, and evidence suggests that tropical countries will be called on to meet much of this demand. Consider, for example, that in developed countries the agricultural land area, including pastures and permanent croplands, decreased by more than 412 million ha (34%) between 1995 and 2007, whereas developing countries saw increases of nearly 400 million ha (17.1%) (14, 42). Moreover, developing countries expanded their permanent croplands by 10.1% during the current decade alone, while permanent cropland areas in developed countries remained generally stable (14). If the agricultural expansion trends documented here for 1980 2000 persist, we can expect major clearing of intact and disturbed forest to continue and increase across the tropics to help meet swelling demands for food, fodder, and fuel.
Avoiding regime shifts is difficult
Conservation magazine’s Journal Watch Online returns from a long hiatus to report on an interesting new paper on the problems of detecting regime shifts by resilience researchers Oonsie Biggs, Steve Carpenter, and W.A. “Buz” Brock (2009. Turning back from the brink: Detecting an impending regime shift in time to avert it. PNAS DOI 10.1073/pnas.0811729106). They write:
Like the stock market, ecosystems can dramatically collapse. But how much advance notice is needed to prevent a natural system meltdown? A paper in Proceedings of the National Academy of Sciences says the answer might be several decades, which means today’s warning systems don’t detect changes nearly far enough in advance.
Using Northern Wisconsin’s sport fishery as a model, University of Wisconsin researchers determined when an ecosystem reaches the brink of an unstoppable shift, then estimated when recovery efforts must start in order to avert collapse. They found that some rapid actions only need short timetables; angling cuts can prevent permanent damage to fisheries even if they’ve been declining for ten years. But other changes, like restoring habitat after too much shoreline development, must start as many as 45 years before ecological health indicators start wobbling.
The problem is, most indicators in today’s early-warning systems can’t detect serious shifts that far out. Even if they could, it might still take policymakers years to enact recovery schemes. Which leads the authors to plea for indicators that work on a longer horizon, and for policy makers to move swiftly once scientists buy them some time.
Are ecosystem service trade-offs relatively common?
A recent paper by Heather Tallis et al. reports the finding that win-win conservation projects — those that aim to achieve both conservation objectives and economic gains — are relatively rare. In this paper (Proc Natl Acad Sci U S A 2008 Jul 15 105(28):9457-64), the authors examine World Bank projects with dual objectives of alleviating poverty and protecting biodiversity and find that only 16% made major progress on both objectives.
These results suggest that trade-offs among ecosystem services may be more common than previously thought. (Fairly interesting since other studies have shown that win-wins are common;however, those studies have generally not considered agriculture/food to be an ecosystem service. Since agriculture is one of the key services that has trade-offs with conservation, it is an important one to consider when assessing the conservation potential in an area.)
Nevertheless, the authors point out that there are strategies for improving management of ecosystem services and human well-being. These include better monitoring of conservation projects’ effects on ecosystem services and human well-being and also improving monitoring of multiple ecosystem services, including the flow of services from one region to another and the effects of markets on provision of ecosystem services.