Four decades of fragmentation

27 09 2017

fragmented

I’ve recently read perhaps the most comprehensive treatise of forest fragmentation research ever compiled, and I personally view this rather readable and succinct review by Bill Laurance and colleagues as something every ecology and conservation student should read.

The ‘Biological Dynamics of Forest Fragments Project‘ (BDFFP) is unquestionably one of the most important landscape-scale experiments ever conceived and implemented, now having run 38 years since its inception in 1979. Indeed, it was way ahead of its time.

Experimental studies in ecology are comparatively rare, namely because it is difficult, expensive, and challenging in the extreme to manipulate entire ecosystems to test specific hypotheses relating to the response of biodiversity to environmental change. Thus, we ecologists tend to rely more on mensurative designs that use existing variation in the landscape (or over time) to infer mechanisms of community change. Of course, such experiments have to be large to be meaningful, which is one reason why the 1000 km2 BDFFP has been so successful as the gold standard for determining the effects of forest fragmentation on biodiversity.

And successful it has been. A quick search for ‘BDFFP’ in the Web of Knowledge database identifies > 40 peer-reviewed articles and a slew of books and book chapters arising from the project, some of which are highly cited classics in conservation ecology (e.g., doi:10.1046/j.1523-1739.2002.01025.x cited > 900 times; doi:10.1073/pnas.2336195100 cited > 200 times; doi:10.1016/j.biocon.2010.09.021 cited > 400 times; and doi:10.1111/j.1461-0248.2009.01294.x cited nearly 600 times). In fact, if we are to claim any ecological ‘laws’ at all, our understanding of fragmentation on biodiversity could be labelled as one of the few, thanks principally to the BDFFP. Read the rest of this entry »





Learning from danger

13 05 2013
Guanaco fleeing
Study vehicle, a group of vicuñas and a guanaco in San Guillermo National Park (San Juan, Argentina) [courtesy of Marco Escudero]. Guanacos and vicuñas are native to South America, and are the ancestors of domesticated llamas and alpacas – which are exploited for their meat, milk and wool. Both species form monotypic genera. They have discontinuous distributions in Argentina, Bolivia, Chile and Peru, with introduced populations in Paraguay (guanaco) and Ecuador (vicuña). Population estimates are > 500,000 (guanaco) and > 300,000 (vicuña), the latter restricted to high-altitude ecosystems. They are ‘Least Concern’ for the IUCN but, given their low population growth rates (fertility = 1 offspring/female/yr), guanacos and vicuñas are targeted by conservation programs in all their native countries.

Many of us might have stumbled twice on the same stone, yet learnt to be wary of future situations of similar risk. Likewise, wild animals can be predisposed to flee when faced with already known predators (or threats in general). The type and magnitude of their evasive response depends on predator distance, speed and body size (1). Regardless, prey need to assess predation risk in a matter of seconds (or even shorter than that), i.e., balancing the benefits and costs of fleeing.

The benefits all boil down to survival, but the costs might include moving away from offspring, loss of access to fresh and abundant food, or spending precious metabolic energy (2). The methods ecologists use to study animal flight behaviour in the wild are rife with nuisances (3), yet they represent a tool for quantifying wildlife stress resulting from a variety of human activities.

Equipped with our modern technological kit (weapons, vehicles, GPS, etc.), humans behave like genuine predators and can trigger the range of flight behaviours displayed by their potential prey. In that context, Emiliano Donadio and Steve Burskirk (4) studied flight behaviour of guanacos (Lama guanicoe) and vicuñas (Vicugna vicugna) in the Argentinean open plains (‘llanos’). They monitored 2 protected areas under weak surveillance and subject to illegal hunting: the Laguna Brava Provincial Reserve and the San Guillermo Biosphere Reserve (treatment = H); and one area free of hunting and only exposed to guided visits with strict entry/exit times: the San Guillermo National Park (treatment = NH). The ecologists did 3 transects per study area. When they encountered a group of camelids, they classified three types of flight behaviour (alert without fleeing, walking away, galloping away), and measured flight time (between vehicle detection and initiation of flight behaviour) and flight distance (between the vehicle and the individuals when initiating flight behaviour). Read the rest of this entry »