To share or spare land? A 25-year debate
By Meine van Noordwijk
The Centre’s chief science advisor reflects on 25 years of research and debate.
First in a series of articles related to the Centre’s history of research and its continuing relevance.
On 13 October 1987, the PhD thesis, ‘Roots, plant production and nutrient use efficiency’, was defended in two separate exams at Wageningen University in the Netherlands.
The thesis had been written jointly by Peter de Willigen and myself. Both of us had to defend a number of chapters, as well as the overall introduction and discussion. Such a joint thesis was possible under the Dutch academic rules, although these rules were rarely applied.
This suggests that the material has not lost its relevance. The thesis as a book has attracted many more citations than even the best peer-reviewed journal paper derived from the content.
At the time of the PhD exam, the hottest issue was directly derived from the title: are plant production and resource use efficiency essentially independent properties (production can be low, intermediate or high in combination with any level of efficiency) or is efficiency essentially positively correlated with production levels?
Our promotor, Prof CT De Wit, an influential member of the CGIAR Science Council, had argued the latter whereas we defended the former.
We quantified the relationship between water and nutrient uptake efficiency (uptake as part of available resources) and root length density, adding a fourth quadrant to the three-quadrant graphical relationship between application, uptake and plant growth, which had been introduced by De Wit.
The inferred correlation of efficiency and yield, as De Wit had proposed, was the core of what we now call ‘land sparing’, ‘segregation’ or the Borlaug hypothesis: from society’s point of view it is best to farm in ways that approximate potential yields per unit area and spare other land for other functions; this will prove to be the most efficient use of resources. In other words, by addressing all production constraints, efficiency and environmental issues will automatically be solved or optimized.
The ‘rebel’ notion we defended—that resource use efficiency (compared at equal total yield) might actually be maximized in less intensive systems, such as ‘ecological agricultural intensification’—was the basis of what is now called a ‘land sharing’ or ‘integration’ hypothesis. It implied that addressing (the lack of) efficiency was a good way to optimize production plus address environmental concerns.
We approached ‘efficiency’ as an empirical issue, open to analysis and theory formation; for De Wit it was a ‘symptom’ to be addressed in other ways: a rather fundamental difference. Our discussions throughout the thesis writing continued during the exam and beyond.
Six years after defending my part (I’m one of the very few people who is second author on their own PhD thesis), I joined the agroforestry research of the International Centre for Research in Agroforestry (branded as the World Agroforestry Centre since 2002) and a large program (ASB Partnership for the Tropical Forest Margins) that was testing the Borlaug hypothesis on the margins of tropical forests.
This brought environmental aspects into the debate beyond water and nutrient use efficiency but the basic conclusion remained the same: there was no intrinsic, generic choice for either sparing or sharing hypothesis but an outcome that depends on specific characteristics of the production system, including tree and crop root architecture.
A first application of the ‘segregate or integrate’ framework that took the intercropping analysis to landscape multifunctionality was presented at the Second Conference of the Parties to the Convention on Biological Diversity, in 1995, in Jakarta, Indonesia.
Recast in ‘sparing versus sharing’ terms, the discussion re-emerged some five years ago, this time capturing a much broader audience.
A recent summary of the debate, ‘Segregate or integrate for multifunctionality and sustained change through landscape agroforestry involving rubber in Indonesia and China’, can be read in Agroforestry: The Future of Global Land Use.
And so it seems that the hot debate of 25 years ago is still relevant and more empirical work is still needed.
Photos courtesy of Kurniatun Hairiah.