November 18, 2013
Land Management Could Save Butterfly Populations
Lee Rannals for redOrbit.com – Your Universe Online
Researchers from Sweden and Germany writing in the journal Nature Conservation reviewed effects of land management on butterfly diversity using historical and current surveys over the past 100 years. The study focused on systematic surveys of butterfly population trends and extinction rates in southern Swedish agriculture landscapes.
Many butterfly populations are closely associated with the agriculture landscape. Scientists say that changes in farming practices and land use can have far-reaching consequences for the success and persistence of butterfly fauna.
Land use in northern Europe has changed markedly with key butterfly habitats, such as hay meadows, disappearing at alarming rates. The grazed, mixed and open woodlands have transformed into dense forests and domestic grazers have been relocated from woodlands to arable fields and semi-natural grasslands. Hay and silage harvest start earlier in the season than before, reducing the time available for larval development.
“As a consequence, considerable areas of traditionally managed grasslands that once were unfertilized, mowed late in summer and then grazed have become intensively used land or abandoned,” the researchers wrote in the journal. “This changed management has had a substantial negative effect on flora and fauna, and many species are declining and are on the verge of regional extinction. Indeed, the declining European semi-natural grasslands are associated with a unique set of species that since long has been adapted to these habitats.”
Change in land use has markedly reduced the availability of nectar resources in the landscape. Researchers also say that current agricultural subsidy systems favoring intensive grazing on the remaining semi-natural grasslands is also adding to these problems for butterflies.
The team said that traditional conservation efforts have focused on plants, but during the last 30 years, butterflies have gained more attention and the knowledge about them is well-established. The scientists believe that relatively minor adjustments to land management could potentially have drastic counteracting effects on the declining butterfly population.
In order to mitigate risks of further species loss and to help recover some of the threatened butterfly populations, the team recommends twelve management measures favorable for butterflies. Some of these examples include later grazing, rotational grazing with parts of semi-natural grasslands grazed only in late summer in some years, and careful choice of grazers.
“Today, abandoned grasslands are very common in less productive areas and might in a near future become transformed into forests. There is an urgent need for immediate action to preserve the most endangered types of grassland vegetation such as unfertilized, mown and lightly grazed areas, as well as to manage the abandoned grasslands before it is too late,” the researchers wrote in the journal.