Earthworms, bees, Ethiopian wild barley, peregrine falcons, orchids, mangrove swamps and tropical rainforest: on the face of it, these might seem a motley collection, but they are all symbols of both the diversity and the fragility of the linkages between agriculture and nature.
Biodiversity is the term commonly used by scientists and policymakers to capture nature’s richness and diversity, but also its biological interdependence. In fact, all species on earth may to a greater or lesser extent be dependent on one another; each species that disappears may weaken the survival chances of another. On a broad scale, tropical forests, for instance, digest carbon dioxide from the atmosphere and produce oxygen. So, without them, our future could be seriously imperilled. And because farming occupies more land than any other human activity in most countries, it should be no surprise to learn that agriculture and biodiversity are interdependent too.
While biodiversity “richness” differs according to climate, terrain, farming practices and so on, farms based on multiple crops and livestock with natural pasture are richer in biodiversity than monocultural farms. But most systems, by seeking to maximise the yield of a limited number of plant and animal species, inevitably weaken and reduce competition from unwanted species.
Farming can affect the worms and soil micro-organisms that play a critical part in maintaining soil fertility, or the bees that provide an important eco-service as pollinators for agricultural crops. The parasitic mite, varroa, in bee populations in North America and Europe has, for example, reduced yields for some crops in affected areas. But in some cases farmers are in a constant battle to control invasive species like weeds and pests that can harm their stock and threaten crop production.
Take the southern maize leaf blight in the early 1970s that led to a 15% fall in US maize yields and an estimated loss to producers and consumers of more than US$2 billion. The crop recovered thanks to help from a Mexican maize variety, but it shows that biological interdependence is not just about preserving wild birds or flowers, but about hard, sustainable, economics. In Australia feral populations of mammals, such as rabbits, dogs and foxes, have inflicted economic losses to farmers through damage to crops, the spread of disease to livestock and the destruction of native wild species.
Farming develops crop species and livestock breeds, as the genetic raw material providing the basis for food production and agricultural raw materials, like cotton. Breeding commercial crop species with wild relatives has also played a vital role in combating pests and diseases. For example, a gene from an Ethiopian wild barley variety has provided protection for the farmed barley crop in North America.
But while farming depends on biodiversity, it is also considered a major contributor to its loss. The intensification of farm production across OECD countries has been associated with the decline in certain wild species, both fauna, such as the peregrine falcon in Europe, and flora such as orchids. In some regions the spread of agriculture has led to the loss of valued wildlife habitats, such as mangrove swamps in the United States and tropical rainforests in Australia. At the same time, farming can enrich society through maintaining and enhancing a variety of wild plant and animal species and habitats, all of which have not just economic or scientific value, but also recreational, even aesthetic advantages, too, such as alpine pastures and water meadows.
One complication is that biodiversity can suffer from invasion of introduced species. These can be beneficial, as in the Mexican maize example, but can be damaging too, whether it be wild mink attacking poultry in Denmark or wire grass spreading in Greece. A US government study estimated economic losses from non-indigenous fauna and flora in the US over the 20th century at US$97 billion. The question of invasion has a new urgency these days, with the development of genetically modified crops and our need to understand their potential effects on local species.
The underlying challenge is how to expand and improve agricultural production – especially given the projected need to increase global food production by over 20% by 2020 – while securing our planet’s biodiversity. Up to now, the main focus of policy in the area of biodiversity has been to protect and conserve endangered species and habitats, but a number of countries are beginning to move toward a more holistic policy approach by developing national biodiversity plans that include agriculture. These plans often reflect the commitments countries have made under the international Convention on Biological Diversity, agreed in 1992, which aims at the conservation of biodiversity, including genetic resources, wild species and habitats.
Part of the task is to quantify the linkages between human activities and biodiversity. As Harvard University specialist, E.O. Wilson, comments, “New indicators of progress are needed to monitor the economy, wherein the natural world and human well-being, not just economic production, are awarded full measure.” In a similar vein the Nobel prize winning economist, Kenneth Arrow, observes, “It would be especially useful to develop better data quantifying the losses of natural capital we currently are experiencing.”
This is not an easy task. Few countries have systematic monitoring systems in place that track trends in biodiversity. In addition, there are formidable scientific difficulties in linking changes in biodiversity associated with agriculture to specific policy measures. To overcome some of these deficiencies the OECD is developing a set of agri-biodiversity indicators.
The first step has been to establish a common agri-biodiversity framework or tool that helps simplify the complexity of agri-biodiversity linkages and identifies suitable indicators to track trends. The framework depicts agriculture in terms of a three-tier, hierarchical structure. The first and basic layer refers to farmland itself, to see if it is expanding or contracting or affecting nearby ecosystems, like forests. The extent of crop and livestock production species – the genetic resources of farming – are also covered in this layer, as is the effect of support species, like earth worms, on soil quality.
The second layer focuses more on structural elements that may affect the ability of a farm to support a varied biodiversity, such as the variability in cropping patterns, field size, and the distribution and extent of uncultivated areas such as ditches, ponds and trees usually associated with a greater biodiversity. This layer also checks for the impact of different farming practices on biodiversity: organic, extensive, intensive and so on.
The final layer assesses the quality of the farming system by finding out how many wild species use it for breeding, feeding and other needs. The richer the biodiversity, the higher the farming quality will be. That means actually counting species, a job for which some governments already earmark budgets.
Perhaps not a spectacular framework, but it should help us answer several key questions. What are the impacts of alternative farming systems, such as organic farming, on sustainable food production capacity? What are the impacts on biodiversity of current farm policies, and in the future, of reducing subsidies to agriculture? And are international interests in biodiversity and trade liberalisation complementary, or in conflict?
Further work will also be necessary to explain and monitor these complex, two-way, dynamic relationships. Still, it is the only way to identify alternative ways to achieve sometimes competing public objectives while not upsetting Earth’s fragile biological system.
* Note: Wilfrid Legg, Ken Ash and Laetitia Reille also contributed to this article.
• OECD (2001), Environmental Indicators for Agriculture Volume 3: Methods and Results, OECD, Paris.
©OECD Observer No. 233, August 2002