The UK is reintroducing bison to improve biodiversity

The Wilder Blean project, like many of its kind, is largely inspired by the work of Dutch ecologist Frans Vera. In his influential book Pasture ecology and forest history, published in 2000, Vera challenges the prevailing view that lowland vegetation in central and western Europe used to be dominated by closed forests. As a result of this assumption, he writes, much credit has been given to agriculture for increasing biodiversity, as grazing livestock produce different types of vegetation. But Vera argues that this theory ignores the influence of wild animals, and particularly large herbivores, which may have played a similar role in creating more diverse landscapes.

To make his argument (which is not without objections), Vera draws on evidence, including the effects of wildebeest grazing in the Serengeti and prehistoric pollen samples, and concludes that conservationists today need to update their frame of reference. He calls for large areas to be kept free from agriculture and forestry and for once wild mammals to be resettled. “Cattle, horses, bison, red deer, elk, roe deer and wild boar must be able to operate as wild animals again,” he writes. “Without these ungulates, the long-term survival of natural diversity is impossible.”

Not all herbivores are the same when it comes to ecosystem engineering. Bison occupy an intermediate position in terms of dietary habits; They are both grazers that eat grass and browsers that engage in woody vegetation such as tree branches. And they eat a lot. “Debarking a tree or shrub for a year or more has a lot more impact than ripping off a few leaves every now and then,” says Kemp. Because of this, several reintroduction projects have introduced bison to mainland Europe, including one in the dunes of Kraansvlak on the Dutch coast, which the Wilder Blean team visited in preparation.

While Kunzmann collects vegetation data on the ground, Robbie Still takes a macro look. As GIS and Remote Sensing Officer for the Kent Wildlife Trust, he is responsible for the project’s engineering – a kind of conservation Q. The team plans to obtain aerial images of the entire site at 20 centimeters resolution by sending up a DJI Matrix drone and methodically flying it over the tree line. “We’re not just zooming around on the remote; It goes up and follows a very pre-planned route,” says Still.

He processes the images with the open source software OpenDroneMap and uses various sensors and tools to obtain information about the vegetation. In addition to overall coverage, it can determine the width of trees by measuring the diameter of their canopy, and their height by measuring the difference between the drone’s position and the objects it is detecting. As the forest used to house conifer plantations, much of it now consists of younger, smaller trees arranged in rigid rows – not ideal for biodiversity. “We’re hoping that it levels out so that it’s much more heterogeneous,” he says.

With the help of multispectral imaging, which records ultraviolet and infrared light in addition to the visible spectrum, Still can even tell whether a tree is a deciduous or coniferous tree based on the color signatures of the leaves: the deeper green of coniferous trees is of the lighter Color palette to distinguish deciduous plants. This imaging could even give an idea of ​​the health of the trees: chlorophyll, the pigment responsible for photosynthesis, absorbs visible light, while plant cells reflect near-infrared light. Algorithms that calculate the difference between the different reflected wavelengths can give an idea of ​​how much photosynthesis a plant is doing – an indicator of its overall fitness.

Still’s team conducted their first drone survey in the spring of 2022, when the trees were still leafy. They will repeat the survey a year later (after the bison arrive) to see what has changed. “Monitoring is incredibly important in ecology, but it’s often overlooked,” says Still. “Not because of an accident, just because of the time.”

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