[新闻]牛津大学研究发现有机种植促进生物多样性

牛津大学的科学家讲述到，在植物、昆虫和动物物种方面，有机农场比传统农场平均多出34%。研究人员研究的数据从30年前开始回溯，发现这种效应随时间保持稳定，丝毫没有减少的迹象。研究发表在本周的《Applied Ecology》学报，当前的94项研究涵盖了184个农场自1989年至今的数据。研究人员使用卫星图像重新分析数据，围绕在物种丰富度方面是否具有重要影响力，对每一个农场的状态进行评估。这项研究由牛津大学的科学家和瑞典农业科学大学完成，资助方为自然环境研究委员会（NERC）。

“我们的研究表明，有机农业，作为一种替代传统的农业，对生物多样性有重要作用及可带来长期的效益，”研究的主要作者、牛津大学植物科学系Sean Tuck说道，“有机方式可能有利于在工业化国家阻止生物多样性的持续丧失。”“在有机农场，传粉类昆虫如蜜蜂，其种类数目比传统农场搞50%，尽管研究只留意于物种丰富度的重要性方面”。

“物种丰富度告诉我们有多少不同的种类，但并没有说到所有生物的总数，”Mr Tuck先生说。“研究生物多样性和物种丰富度有许多方法，而且容易观测，这样可以提供一个的有效的起点。一般来说，物种丰富度高通常预示具有各种功能不同的物种。以蜜蜂为例，物种丰富度会告诉我们有多少不同种类的蜜蜂在每个农场而不是蜜蜂总数量。”

周围更密集耕种的土地，有机农场对其物种丰富度的影响更大，特别是那些大面积的耕地。耕地是指被作物占用、在同一耕种年进行播种和收获的土地；如作物可以是小麦或大麦。

“我们发现在密集种植区，有机农场影响物种的丰富度更为显著，”该研究的主要作者、牛津大学植物科学系琳赛特恩布尔博士说，“这是有效的方式，因为每一个有机农场的生物多样性带来的好处将被稀释在有机农场群，类似说在覆盖农药的传统领域的“大海”上，冒出了一个有机“岛”给丰富的物种提供了一个栖息地。对传粉者这种影响是最微弱的，这可能是因为传粉昆虫可能常接触到附近使用农药的农场所造成的。”

通过数据分析，有机农业的物种丰富度的平均指数分布在26%~43%之间，影响总物种丰富度的因素存在显著差异。这种变化可以归结为与采用不同耕作方式、选择确定为“有机”的土地等一系列相关因素有关。

       附原文：

       On average, organic farms support 34% more plant, insect and animal species than conventional farms, say Oxford University scientists.

       Researchers looked at data going back 30 years and found that this effect has remained stable over time and shows no signs of decreasing.

       'Our study has shown that organic farming, as an alternative to conventional farming, can yield significant long-term benefits for biodiversity,' said Sean Tuck of Oxford University's Department of Plant Sciences, lead author of the study. 'Organic methods could go some way towards halting the continued loss of diversity in industrialised nations.'

       For pollinators such as bees, the number of different species was 50% higher on organic farms, although it is important to note that the study only looked at 'species richness'.

      'Species richness tells us how many different species there are but does not say anything about the total number of organisms,' said Mr Tuck. 'There are many ways to study biodiversity and species richness is easy to measure, providing a useful starting point. Broadly speaking, high species richness usually indicates a variety of species with different functions. Taking the example of bees, species richness would tell us how many different species of bee were on each farm but not the total number of bees.'

       The study, published this week in the Journal of Applied Ecology, looked at data from 94 previous studies covering 184 farm sites dating back to 1989. The researchers re-analysed the data using satellite imagery to estimate the land use in the landscape surrounding each farm site to see if this had an impact on species richness. The study was carried out by scientists at Oxford University and the Swedish University of Agricultural Sciences, and was partly funded by the Natural Environment Research Council (NERC).

       Organ ic farms had a bigger impact on species richness when the land around them was more intensively farmed, particularly when it contained large tracts of arable land. Arable land is defined as land occupied by crops that are sown and harvested in the same agricultural year, such as wheat or barley.

       'We found that the impacts of organic farms on species richness were more pronounced when they were located in intensively farmed regions,' said Dr Lindsay Turnbull of Oxford University's Department of Plant Sciences, senior author of the study. 'This makes sense because the biodiversity benefits of each organic farm will be diluted in clusters of organic farms compared to an organic "island" providing rich habitats in a sea of pesticide-covered conventional fields. This effect was weakest in pollinators, which may be because pollinators are likely to visit neighbouring farms and could be affected by pesticides there.'

      The impact of organic farming on total species richness varied significantly across the data, with the average gain in species richness varying between 26% and 43%. This variation could be down to a number of factors relating to regional variation in farming practices and definitions of 'organic'.

      'Some conventional farms will intensively spray pesticides and fertilisers whereas others will use mixed methods of crop rotation and organic fertilisers with minimal chemical pesticides,' said Dr Turnbull. 'There are also regional differences in farming practices, and the majority of the studies in our data were in developed nations with long histories of farming such as those in Western Europe. There, some wildlife have thrived in extensively managed farmland but are threatened by agricultural intensification. However, in developing nations there is often great pressure on the land to provide enough food for local people, resulting in the conversion of natural habitat to farmland. In such cases the benefits of organic farming are less clear, as this may require more land to achieve the same yield as conventional farming.

       'More research is needed on the impact of organic farming in tropical and subtropical regions. For example, there are no studies on organic bananas or cocoa beans, two of the most popular organic products found in European supermarkets. At present, we simply cannot say whether buying organic bananas or chocolate has any environmental benefit.

    laiyuan:http://www.ox.ac.uk/media/news_stories/2014/140204.html