We have captured no evidence for the effects of erecting predator-proof fencing around important breeding sites for waders on farmland wildlife.
'No evidence' for an action means we have not yet found any studies that directly and quantitatively tested this action during our systematic journal and report searches. Therefore we have been unable to assess whether or not the action is effective or has any harmful impacts. Please get in touch if you know of such a study for this action.
A study in Scotland recorded lower lice numbers on Atlantic salmon in cages using a fallowing system. Another study in Australia found no difference in mortality from Amoebic Gill Disease in cages where a fallowing system had been used.
Parasitism:One of two replicated, controlled studies (one also randomised) from Japan and the USA found greater parasitism of pests by natural enemies when ants were excluded from trees. The other study found greater parasitism at one site but no effect at another. Natural enemies: Five studies (including four randomised, replicated, controlled trials) from Japan, Switzerland and the USA found effects varied between natural enemy species and groups, sampling dates, sites, crop varieties and ground cover types beneath trees. Pests: Three of seven studies (including four randomised, replicated, controlled trials) found fewer pests and another found fewer pests at times of peak abundance only. One study found mixed effects depending on date and other actions taken simultaneously (predator attractant and ground cover treatments). One study found no effect. Damage and tree growth: One study found no effect on damage to tree foliage but one study found greater tree growth. Ants: Six studies found that glue or pesticide barriers reduced ant numbers in tree or vine canopies. One study found that citrus oil barriers had no effect.
Two replicated (one controlled) studies from the USA found higher species richnesses on sites with grazers excluded; a replicated and controlled study from Argentina found lower species richness in ungrazed sites and a study from the USA found no difference.
Seven studies from the USA (three controlled, two replicated) found that overall bird abundance, or the abundances of some species were higher in sites with grazers excluded; seven studies from the USA and Argentina found that overall abundance or the abundances of some species were lower on sites without grazers, or did not differ between treatments.
Three studies from the USA investigated productivity and found it higher in sites with grazers excluded. In one study this difference was only found on improved, not unimproved pastures.
Seven studies (including four replicated controlled trials of which one also randomized, and a review) from Ireland, Poland and the UK looked at the effects of excluding livestock from semi-natural habitats. Three studies (including one replicated controlled and randomized study) from Ireland and the UK found that excluding livestock benefited plants and invertebrates.
Three studies (one replicated controlled and one replicated paired sites comparison) from Ireland and the UK found that excluding grazing did not benefit plants or birds.
Two studies (one replicated and controlled, one review) from Poland and the UK found that the impact of excluding grazing as a tool in habitat restoration was neutral or mixed.
We captured four studies examining the impacts of fertilizing grasslands, all from the UK and investigating grazing by geese Anser and Branta spp. Two studies found that more geese grazed on areas that were fertilised compared with control areas. Two studies found that cut and fertilised areas were used more than control areas. One study found that fertilised areas were used less than re-seeded grasslands.
One study found that fertilisation affected grazing at applications of 50 kg N/ha, but not 18 kg N/ha. One study found that grazing rates only increased with applications of up to 80 kg.N/ha.
Biodiversity:One randomized, replicated study from Spain found that cover crops increased bacterial numbers and activity.
Erosion: Two studies from France and the USA showed reduced erosion under cover crops. One controlled study showed that soil stability was highest under a grass cover, and one randomized replicated study found that cover crops reduced soil loss.
Soil organic matter: Two controlled trials from India and South Africa (one also randomized and replicated) found that soil organic matter increased under cover crops, and one trial from Germany found no effect on soil organic matter levels.
Biodiversity: One controlled, randomized, replicated experiment in Martinique found that growing cover crops resulted in more diverse nematode communities. One replicated trial from the USA found greater microbial biomass under ryegrass compared to a ryegrass/vetch cover crop mix.
Soil structure:Three randomized, replicated studies from Denmark, Turkey and the UK found that growing cover crops improved soil structure and nutrient retention. One trial found higher soil porosity, interconnectivity and lower resistance in soil under cover crops, and one found reduced nitrate leaching.
Soil organic carbon: One replicated study from Denmark and one review based mainly in Japan found increased soil carbon levels under cover crops. One study also found soil carbon levels increased further when legumes were included in cover crops.
Soil organic matter: One replicated study from Denmark and three controlled, randomized, replicated studies from Australia and the USA measured the effect of growing cover crops. Three found increased nitrogen levels under cover crops, three found increased carbon, and one found increased nitrates. One trial showed that they increased regardless of whether those crops were legumes or not. Two studies from Europe (including one controlled, replicated trial) found no marked effect on soil organic matter levels.
Yield:One replicated trial from the USA found higher tomato yield from soils which had been under a ryegrass cover crop.
Natural enemies: Four studies from China, Germany, India and Kenya tested the effects of growing plants that produce chemicals that attract natural enemies. Three (including one replicated, randomised, controlled trail) found higher numbers of natural enemies in plots with plants that produce attractive chemicals, and one found that the attractive plant also attracted natural enemies in lab studies. One found no effect on parasitism but the plant used was found not to be attractive to natural enemies in lab studies. Pests: All four studies found a decrease in either pest population or pest damage in plots with plants that produce chemicals that attract natural enemies. Yield:One replicated, randomised, controlled study found an increase in crop yield in plots with plants that produce attractive chemicals.
Weed weight and cover: Nine studies from Australia, Slovakia, the UK and the USA tested the effects of planting species to compete with weeds. All (including four replicated, randomised, controlled trials) found reduced weed plant weight or ground cover, although two found this only in some years or conditions. Weed reproduction and survival:Five studies (including three replicated, randomised, controlled trials) also found that competition reduced weed reproduction, survival or both. One of these found an effect only in one year only.