A meta-analysis drawing on 184 observations from 94 studies has found that, on average, organic farms are home to 34 per cent more plants, insects and other animal species than conventional farms. The research was conducted by Oxford University and published in the journal Journal of Applied Ecology. This result reflects data collected over approximately 30 years of surveys, mostly from so-called industrialised countries. The study's authors also highlighted how organic farms have a greater positive effect on biodiversity precisely in the most intensively farmed areas, providing rich habitats and the absence of synthetic pesticides.

Organic farming, greater biodiversity

The greater biodiversity that characterises organic farms is stable over time and shows no sign of declining. With regard to pollinating insects, such as bees, the number of different species is 50 per cent higher on organic farms. "Our studies have shown that organic farming, as an alternative to intensive farming, delivers significant long-term benefits for biodiversity – wrote Sean Tuck, the lead author of the Oxford University research – so it is a way of countering the ongoing loss of animal and plant species that is affecting industrialised nations."

What studies dating back to 1989 reveal

The researchers analysed data from 94 previous studies covering 184 farming areas over a period of time starting from 1989. They then cross-referenced these with satellite imagery to analyse the impact of cultivation and its extent on the number of species on the ground. The more land was farmed using intensive or conventional methods — especially with large stretches of tilled soil — the fewer species were found. By contrast, organic farming consistently recorded strong growth in biodiversity, with increases ranging from 26 to 43 per cent.

Where and how crops are grown makes a difference

The variation is due to the number of factors relating to locations and farming methods in use, as well as to the definition of "organic" in the different countries examined. On some conventional farms, fields are sprayed with pesticides and fertilisers; on others, crop rotation and integrated pest management are used more widely; there are also regional differences and the influence of years of farming, given that most of the studies were collected in countries with a long agricultural history, such as those of western Europe.