By Joern Fischer
There is only a handful of publications still in the pipeline for our project on sustainable development in Central Romania — timely indeed, since funding finishes at the end of 2015! Today I’d like to briefly highlight a new paper that takes a first stab at synthesising what we’ve learnt in five years of research. This paper just came out in the new journal Ecosystem Health and Sustainability, which is published by the Ecological Society of America together with the Ecological Society of China. The paper is led by Ine Dorresteijn, and synthesises drivers of biodiversity.
What causes Transylvania’s exceptional biodiversity? We came up with seven underlying drivers or processes. While these are specific to Transylvania, it seems likely that there are parallels to other traditional farming landscapes elsewhere.
1. Similar proportions of three main land-use types support a rich regional species pool. It is relatively well-known that the effects of area loss and isolation start to have severely negative synergistic effects on biodiversity when the proportion of a given land cover type is low. Some have argued around 30% is good, and below that, things start to increasingly fall apart. If that is so, this is a potential explanation for why biodiversity is so high in Transylvania — there is about 30% of forest cover, as well as about 30% of grassland; plus another approximately 30% of arable land (including field margins). So, whether you’re a forest species, a grassland species, or a species adapted to agriculture, there’s likely to be enough space for you in Transylvania.
2. Landscape complementation and supplementation facilitate the persistence of species outside their core habitat. Often, land covers in Transylvania are juxtaposed in ways that species can use more than one kind of land cover. For example, bears primarily inhabit forest, but they also come out and forage in the pastures (e.g. for ant larvae, a protein source). Similarly, some butterflies lay their eggs in grassland, but also forage in the arable mosaic; and woodpeckers move been forests and wood pastures.
3. Gradients of woody vegetation cover provide important structural diversity. Woody vegetation in farmland is generally believed to be good for biodiversity. And for many species, that’s true, and they benefit from the trees and shrubs retained throughout Transylvanian farmland. But for other species, it’s entirely treeless, open grasslands that constitute high quality habitat. Luckily, those species also find their place in Transylvania — there’s a whole gradient of woody vegetation present throughout the farming mosaic, from entirely devoid of trees and shrubs, to quite a bit of structural complexity. This mix means many different kinds of species can use the landscape.
4. Gradients in land-cover heterogeneity provide a diversity of niches. Structural complexity (trees and shrubs) is one important (vertical) feature of landscapes — another is the spatial variability of land covers, or heterogeneity. Here, too, many species benefit from the high variability in many locations, especially in the arable mosaic — small fields with distinctly different margins are useful for many species. But again, the opposite is also present, namely large areas of relatively homogenous land cover. This is the case for some forest patches, for example, and some pastures. Species that need a lot of space of “the one thing” can use such more homogenous areas.
5. Traditional land-use practices underpin landscape heterogeneity, traditional landscape elements, and human–carnivore coexistence. The ecological and land cover patterns that we see have resulted from traditional land use practices — including moving hay meadows by hand, ploughing fields by horse, and using guarding dogs to defend livestock against bears and wolves. To maintain the land cover pattern thus requires thinking about whether and how these traditional practices can be maintained.
6. Top-down predator regulation may foster biodiversity in traditional farming landscapes in some instances. Central Romania is a cultural landscape — but it’s also a wild landscape with bears and wolves. While humans structure the ecosystem in predictable ways, top carnivores also have retained an important influence. For example, they influence the kinds of herbivores (red deer vs. roe deer) that are found in different parts of the landscape; which in turn, is likely to influence vegetation dynamics.
7. Cultural ties between humans and nature support biodiversity conservation. Many Transylvanians still know their ecosystems very well, including the benefits and dis-benefits. This knowledge is deeply embedded in Transylvanian culture. Smallholder farming to many people is not just a job, but a “good” way of being — an ethic of working the land prevails among many local villagers. Maintaining biodiversity requires an understanding of how people are linked to the natural environment. Otherwise, well-intentioned policy measures (such as subsidies) may actually backfire in the long run.
These drivers range from proximal to more ultimate, from tangible towards fuzzy, and from more ecological to more social. The paper analyses in some more detail how this understanding can inform biodiversity conservation — it’s open access, and you can download it here.