Importance of Small Forest Fragments in Agricultural Landscapes for Maintaining Orangutan Metapopulations

Historically, orangutans (Pongo spp.) lived in large contiguous areas of intact rainforest. Today, they are also found in highly modified and fragmented landscapes dominated by oil palm or industrial timber plantations; a situation that calls for new conservation approaches. Here we report signs of orangutan presence in more than 120 small forest fragments of less than 500 ha in size and isolated in extensive oil palm plantations across Borneo. We confirmed the long-term presence of adult resident females with dependent young in 42% of the fragments assessed by ground survey (n=50), and the regular sightings of males traveling across the landscape. We argue that orangutans using and living in small isolated forest patches play an essential part in the metapopulation by maintaining gene flow among larger sub-populations distributed across multiple-use landscapes. In some cases, translocations may be necessary when the animals are in imminent danger of being killed and have no other refuge. However, the impacts of removing animals from spatially dispersed metapopulations could inadvertently decrease critical metapopulation functionality necessary for long-term viability. It is clear that orangutans need natural forest to survive. However, our findings show that forest fragments within agricultural landscapes can also complement conservation areas if they are well distributed, properly connected and managed, and if orangutan killing is prevented. Efforts to better understand the dynamics and the functionality of an orangutan metapopulation in forest-farmland landscape mosaics characteristic of the Anthropocene are urgently needed to design more efficient conservation strategies for the species across its range

Evaluating a free ion activity model applied to metal uptake by Lolium perenne L. grown in contaminated soils.

We investigated several formulations of the free ion activity model (FIAM) as a means of describing plant uptake of soil Cd and Zn from contaminated soils. Lolium perenne was grown on a range of urban and metal-spiked agricultural soils selected to provide a wide range of Cd and Zn concentrations, pH values and other physico-chemical properties. Plants were grown under controlled conditions and above-ground biomass was harvested at regular intervals. Concentrations of Cd and Zn in the grass were compared with estimates of metal capacity (total or radio-labile metal content in the soil) and intensity (metal concentration in the soil solution or free divalent ion activity). The results suggested that capacity terms alone were poor predictors of plant metal uptake (r2 values between 0.001 and 0.43), while metal ion intensity provided quite reasonable predictions of the variation observed for several harvests of the grass (r2=0.60–0.87). Soil solution-to-plant transfer factors were highly pH-dependent which may suggest significant competition between trace metals and protons for sorption sites on roots. However, resolution of this question was confounded because of the strong co-variance between pH and p(M2+) in the soil pore water. Thus the influence of pH could not be separated from the effect of changing metal ion activity on uptake rate. Other possible effects on metal uptake such as dilution from increased biomass during growth and competition for uptake between different metal ions (Zn vs. Cd), or with Ca2+, appeared to play very minor roles in determining bioavailability. Several formulations of the FIAM failed to provide a consistently superior prediction of metal uptake when compared to purely empirical regression with pH and p(M2+) within the range of the data used to parameterise the models