By Joern Fischer
This blog entry comes from Glasgow, where I’m currently attending the 2012 Meeting of the European Section of the Society for Conservation Biology.
This morning, one of the nicer talks I saw was by Patricia Rogrigues. She investigated the change of ecosystem services in an area in Portugal over the last few decades; in which much agricultural land had been abandoned. A key question was: as provisioning services declined, did regulating services and biodiversity increase? Using INVEST and other tools, she looked at changes in agricultural production through time (provisioning), as well as the regulating services carbon sequestration (four carbon stocks considered) and sediment retention. Using the countryside species-area-relationships (Pereira and Daily 2006), they estimated biodiversity for plants and animals.
Patricia found that both human population and agricultural land had declined since the 1960s, and tall shrublands were replacing arable fields. Carbon storage across the landscape, however, had not changed very much; mostly because most carbon was actually stored in forested parts, which did not change very much. While tall shrubs store more carbon than arable land, this difference is relatively small. Soil conservation, on the other hand, increased much more strongly – with far less sediment being transported in the landscape now compared to the 1960s. For biodiversity, the results were complex: obviously, specialists of arable land declined, whereas those specializing in tall shrubland increased.
The bottom line: decreases in provisioning services did lead to an increases in regulating services; with mixed biodiversity effects. Overall, I thought this was a nice example of looking at trade-offs in ecosystem services through time! I also note that biodiversity effects would have been much more positive if the arable system studied had not been quite extensive to start with (i.e. no wonder there isn’t much of a gain by abolishing agriculture which actually is not very harmful to start with!).
Another nice talk came from Tom Brereton. He talked about conserving butterflies through agri-environment schemes in England. He started by highlighting that approximately 90% of British butterflies breed in some kind of agricultural land in at least part of their range – so agricultural land is vitally important. The British butterfly monitoring program, since the 1970s has now surveyd butterflies across something like 1500 sites. It clearly indicates that butterfly numbers are going down, both for specialist and widespread species. What, Tom asked, was the role of agri-environment schemes in halting such declines?
In a nutshell, it appears that “priority species” typically perform better at agri-environment sites than elsewhere. While the decline of priority species at sites not targeted by agri-environment schemes is continuing unhalted, recent monitoring data shows that in areas targeted by agri-environment schemes, priority specie are in fact no longer declining. This is good news, given some of the negative sentiments currently around about agri-environment schemes!
Notably, Tom highlighted that some species are continuing to decline, throughout the country. He speculated that some of the management options funded were not tailored well enough to some of the species that are still declining – hence they are not effective. Depending on the target species, key issues relate to getting right the structural variety in sward, availability of summer nectar, and the presence (or absence) of shrubs.