UK reintroduces bison to boost biodiversity

The Wilder Blean project, like many of its kind, is largely inspired by the works of the Dutch environmentalist Frans Ver. In his influential book Pasture ecology and forest history, published in 2000, Vera challenges the common belief that lowland vegetation in Central and Western Europe was once dominated by closed forests. As a result of this assumption, he writes, agriculture has been given much of the credit for increasing biodiversity because livestock grazing creates different types of vegetation. But Vera argues that this theory ignores the influence of wild animals, and especially large herbivores, which may have played a similar role in creating more diverse landscapes.

To make his case (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 the release of large areas from agriculture and forestry, as well as the reintroduction of once wild mammals. “Cattle, horses, bison, red deer, elk, roe deer and wild boar will have to work as wild animals again,” he writes. “Without these ungulates, the survival of natural diversity is impossible in the long term.”

Not all herbivores are created equal when it comes to ecosystem engineering. In terms of food habits, bison occupy an intermediate place; they are both grazers, eating grass, and browsers, engaging in woody vegetation such as tree branches. And they eat a lot. “Debarking a tree or shrub over a period of a year or several years has a much greater effect than removing leaves once in a while,” says Kemp. For this reason, several wildlife restoration projects in continental Europe have introduced bison, including one in the Kraansvlak dunes on the Dutch coast, which the Wilder Blean team visited as part of the preparation.

While Kunzman collects data on the vegetation on the ground, Robbie Steele takes a macro view. As Kent Wildlife Trust’s GIS and Remote Sensing Officer, he is in charge of the technology on the project – a kind of conservation Q. The team plans to obtain aerial photographs of the entire site at a resolution of 20 centimeters by sending a DJI Matrice drone to fly methodically above the tree line. “We don’t just scale with a remote control; it goes up and follows a pre-planned route,” says Still.

It will process images using open source software OpenDroneMap, using a variety of sensors and instruments to collect information about vegetation. In addition to overall coverage, it can determine the width of trees by measuring their crown diameter and height by measuring the difference between the drone’s position and the objects it senses. Given that the forests used to have conifer plantations, most of them now consist of younger, smaller trees arranged in solid rows, which is not ideal for biodiversity. “We’re hoping it will level out, so it’ll be much more heterogeneous,” he says.

Using multispectral imaging that captures ultraviolet and infrared light as well as the visible spectrum, Still can even determine whether a tree is deciduous or coniferous based on the color characteristics of the leaves: the deeper green of conifers can be distinguished from the lighter palette of deciduous plants. This image can even give a sense of the trees’ health: 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 provide insight into how much a plant is photosynthesizing—an indicator of its overall fitness.

Still’s team conducted their first drone survey in the spring of 2022, when the trees were blooming. They will repeat the survey in a year (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 any oversight, just because of time.”