Does organic farming benefit biodiversity

Summary 1. Increasing concern over the environmental impact of agriculture in Europe has led to the introduction of agri-environment schemes. These schemes compensate farmers financially for any loss of income associated with measures that aim to benefit the environment or biodiversity. There are currently agri-environment schemes in 26 out of 44 European countries. 2. Agri-environment schemes vary markedly between countries even within the European Union. The main objectives include reducing nutrient and pesticide emissions, protecting biodiversity, restoring landscapes and preventing rural depopulation. In virtually all countries the uptake of schemes is highest in areas of extensive agriculture where biodiversity is still relatively high and lowest in intensively farmed areas where biodiversity is low. 3. Approximately $ 24·3 billion has been spent on agri-environment schemes in the European Union (EU) since 1994, an unknown proportion of it on schemes with biodiversity conservation aims. We carried out a comprehensive search for studies that test the effectiveness of agri-environment schemes in published papers or reports. Only 62 evaluation studies were found originating from just five EU countries and Switzerland (5). Indeed 76% of the studies were from the Netherlands and the United Kingdom, where until now only c . 6% of the EU agri-environmental budget has been spent. Other studies were from Germany (6), Ireland (3) and Portugal (1). 4. In the majority of studies, the research design was inadequate to assess reliably the effectiveness of the schemes. Thirty-one percent did not contain a statistical analysis. Where an experimental approach was used, designs were usually weak and biased towards giving a favourable result. The commonest experimental design (37% of the studies) was a comparison of biodiversity in agri-environment schemes and control areas. However, there is a risk of bias if either farmers or scheme co-ordinators select the sites for agri-environment schemes. In such cases the sites are likely to have a higher biodiversity at the outset compared to the controls. This problem may be addressed by collecting baseline data (34% of studies), comparing trends (32%) or changes (26%) in biodiversity between areas with and without schemes or by pairing scheme and control sites that experience similar environmental conditions (16%). 5. Overall, 54% of the examined species (groups) demonstrated increases and 6% decreases in species richness or abundance compared with controls. Seventeen percent showed increases for some species and decreases for other species, while 23% showed no change at all in response to agri-environment schemes. The response varied between taxa. Of 19 studies examining the response of birds that included a statistical analysis, four showed significant increases in species richness or abundance, two showed decreases and nine showed both increases and decreases. Comparative figures for 20 arthropod studies yielded 11 studies that showed an increase in species richness or abundance, no study showed a decrease and three showed both increases and

How effective are European agri‐environment schemes in conserving and promoting biodiversity?

What determines the number and size of the seeds produced by a plant? How often should it reproduce them? How often should a plant produce them? Why and how are seeds dispersed, and what are the implications for the diversity and composition of vegetation? These are just some of the questions tackled in this wide-ranging review of the role of seeds in the ecology of plants. The authors bring together information on the ecological aspects of seed biology, starting with a consideration of reproductive strategies in seed plants and progressing through the life cycle, covering seed maturation, dispersal, storage in the soil, dormancy, germination, seedling establishment, and regeneration in the field. The text encompasses a wide range of concepts of general relevance to plant ecology, reflecting the central role that the study of seed ecology has played in elucidating many fundamental aspects of plant community function.

The ecology of seeds

. Ecologists need a common language of plant traits in order to make comparisons across regions and scales, pool data, and maximize the utility of the data. To develop such a set of traits we began with the primary challenges faced by plants: dispersal, establishment, and persistence in order to identify fundamental traits. Most of these traits are hard to measure, but advances in comparative ecology have suggested a number of easy to measure analogs. Unfortunately, some of the fundamental traits have no simple analog. The common core list includes: seed mass, seed shape, dispersal mode, clonality, specific leaf area, leaf water content, height, above-ground biomass, life history, onset of flowering, stem density, and resprouting ability. Most of the traits can be measured quantitatively, but several traits on the list must still be measured qualitatively due to logistical problems or lack of an easy analog. Key problem areas include: dispersal ability, capacity for vegetative spread, germination, palatability, plasticity, and all the various below-ground traits. Comparative studies need to address these problem areas. The common core list is suggested as a common starting point for studies of functional ecology. The idiosyncrasies of regional floras and specific research agendas will dictate which traits can be ignored and those that need to be added.

http://traits-dgs.nceas.ucsb.edu/workspace/readings/Weiher_etal_1999.pdf/attachment_download/file

Challenging Theophrastus: A common core list of plant traits for functional ecology

Species diversity has declined in ecosystems worldwide as a result of habitat fragmentation, eutrophication, and land-use change. If such decline is to be halted ecological mechanisms that restore or maintain biodiversity are needed. Two long-term field experiments were performed in native grassland to assess the effects of fire, nitrogen addition, and grazing or mowing on plant species diversity. In one experiment, richness declined on burned and fertilized treatments, whereas mowing maintained diversity under these conditions. In the second experiment, loss of species diversity due to frequent burning was reversed by bison, a keystone herbivore in North American grasslands. Thus, mowing or the reestablishment of grazing in anthropogenically stressed grasslands enhanced biodiversity.

https://science.sciencemag.org/content/sci/280/5364/745.full.pdf

Modulation of Diversity by Grazing and Mowing in Native Tallgrass Prairie

Experiments on the restoration of species-rich meadows in The Netherlands

1. A comparative study was carried out on nitrogen flows in two meadow ecosystems that were similar at the beginning of the experiment. In the wet meadow, groundwater levels had been raised and in the dry meadow no changes in the original groundwater levels had been imposed. 2. Annual nitrogen mineralization and nitrogen accumulation in above-ground biomass were reduced by c. 20in the wet meadow as compared with the dry meadow. In the dry compartment the peak in nitrogen mineralization was reached in spring, whereas in the wet compartment the peak was reached in summer. 3. In the wet compartment a smaller fraction of the ammonium produced was oxidized to nitrate than in the dry compartment (60losses through denitrification were similar (about 17 kg N ha -1 year -1 ). During the summer, however, denitrification was greater in the wet compartment. During the winter denitrification increased sharply, because of nitrate accumulation in the soil at the end of the growing period and was greater in the dry compartment. 5. The nitrogen balance of the two meadow ecosystems shows that the inputs through atmospheric deposition and the outputs through hay removal are quantitatively the most important components of the nitrogen balance. Raising groundwater levels led to less nitrogen accumulation in the aboveground biomass and, thus, to smaller nitrogen outputs through hay removal.

A comparative study of nitrogen flows in two similar meadows affected by different groundwater levels

Germination of Six Grassland Herbs in Microsites with Different Water Contents

The importance of relative growth rate and associated traits for competition between species during vegetation succession

An experiment was carried out at the Veenkampen, the application of fertilizers being stopped. Two possible tools were studies for the restoration of species rich grassland communities: removing nutrients through hay or sod removal and raising the groundwater level

M.J.M. Oomes

Papers

Experiments on the restoration of species-rich meadows in The Netherlands

A comparative study of nitrogen flows in two similar meadows affected by different groundwater levels

Germination of Six Grassland Herbs in Microsites with Different Water Contents

The importance of relative growth rate and associated traits for competition between species during vegetation succession

Restoration of species-rich grassland communities