New research from the United States has shown that a branch of sustainable farming can benefit farmland bird populations, which are threatened in many parts of the world.

Researchers from the University of Utah said that moves in many parts of the world to replace forests with open farmland could further accelerate the decline of a number of bird species. Wooded "shade" plantations which produce coffee and chocolate and natural forests which promote greater bird diversity are being replaced by ranches and farmland.

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‘Agroforests,’ in which crops are grown under trees, support diversity and numbers in bird species. The lack of suitable habitat in Europe, where land is extensively and intensively farmed, is thought to be a major contributing factor to the decline of a variety of bird species. Previously healthy populations of a number of farmland birds have dropped by as much as 90 per cent since 1980.

According to data from BirdLife International and the European Bird Census Council, over the same period, Europe’s population of farmland birds has fallen by over 300 million. This represents around a 50 per cent reduction of the total population.

Researchers behind the Utah study revealed the problem is not confined to Europe; many migratory birds that breed in the United States are in decline, despite legislation aimed at their protection. Whilst environmental problems local to the United States undoubtedly contribute to this, the decline is also thought to be “due to problems in their wintering grounds in Latin America, such as loss of habitat and intensification of agriculture."

Utah bird study

The Utah researchers explained that a reduced number of bird species and shifts in the populations of various types of birds may impact on sensitive "ecosystem services" which birds provide to people, such as eating insect pests, spreading seeds and pollinating crops.

Study author and professor of biology Çağan H. Şekercioğlu, said of the study, which focused on tropical agricultural landscapes, "We found that agroforests are better overall for bird biodiversity in the tropics than open farms. This doesn't mean people should farm in intact forests, but if you have the option of having agroforest versus open farmland, that is better for biodiversity, with shade coffee and shade cacao being the prime examples."

Professor Şekercioğlu's study was published this month in the Journal of Ornithology. He will also present his findings on agroforestry and biodiversity at the Ecological Society of America's annual meeting in Portland, Oregon on 9th August.

The professor said that, whilst the products of agroforestry can sometimes cost more, due to the process’ higher labour intensity, the crops produced by such measures often carry social as well as environmental benefits; he explained such products are "usually better for the farmers' income as well."

The Utah study built on evidence gathered from over 40 localised studies which examined bird communities in forests, agroforests and open agricultural areas from around the world. It investigated 6,093 bird species in all. Professor Şekercioğlu found, "The global analysis of all the birds species mostly agrees with the findings of detailed local bird studies."

Şekercioğlu warned of the potential adverse effects which can result from disrupting natural ecosystems, "As you go to more and more open agriculture, you lose some bird groups that provide important ecosystem services like insect control, seed dispersal and pollination, while you get higher numbers of granivores [seed and grain eaters] that actually can be crop pests."

However, he added, "It is possible you may lose a lot of species, but some of the remaining species increase in number and can compensate and for the decline in ecosystem services provided by the lost species. [Whether a decline in species translates to a decline in provision of ecosystem services] is one of the biggest questions in ecology."

Although professor Şekercioğlu called for more widespread adoption of agroforestry to support threatened bird species throughout the world, he stressed that conservation efforts and environmental protection should be tantamount. Referring back to his own study he said, "As tropical forest is converted to increasingly open types of agriculture, hundreds of endangered bird species are being lost. Tropical forest is the only refuge for thousands of bird species and hundreds of endangered bird species. Although agroforest is better than open farmland, at the end of the day intact tropical forest is the only suitable habitat for thousands of bird species."

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