Capturing change in the Arctic.

How drones help us understand the impact of environmental change on plant communities.

Satellites have revolutionised our understanding of our planet and drones are on track to deliver the next transformation in environmental monitoring. Remote, harsh habitats like the Arctic can now be studied in increasing detail and, for the past 40 years, satellite and aerial images have captured the cyclical change between seasons. The images have also captured rapid shrub expansion all around the pole, a visible sign of the impact warming temperatures are having on our planet.

Recently, I had the opportunity to meet Jakob Assmann, a PhD candidate from the University of Edinburgh who’s spent two summers flying drones in the Arctic as part of a long-term study that’s investigating how climate change is altering plant communities and ecosystem processes. Curious to learn more about the role drones have in his work and the images he’s collected, we talked over coffee in Cambridge.

Jakob in the field with a butterfly and one of his drones. Credit: Sandra Angers-Blondin.
“Big changes are happening in the Arctic,” warns Jakob. “On top of the rapid decline in sea-ice and glacial melt, coastal erosion is happening so fast in Alaska that people have started building their homes on skids so they can pull them back from the coast in winter time. At our research site in the Canadian Yukon, ancient artifacts, like wooly mammoth tusks and pleistocene horse bones, are being spat out by the ice as it melts. Plants are becoming more productive as the summers last longer. All these events are happening because the region is warming up rapidly — faster than anywhere else on the planet.”

Although we’re still learning exactly what role plants in the Arctic might have in reducing or contributing to global warming, the greening of the Arctic is one of the observed global biological changes that can be attributed to man-made climate change with a high degree of confidence. Images taken by satellites, and now drones, are being compiled into a long-term record that tracks these changes in plant cover in the Arctic.

Team Shrub — the study group that Jakob is a part of — is contributing to a research programme that’s been monitoring plants in the Arctic for over 18 years. Amongst others, they monitor arctic willow (Salix arctica), mountain avens (Dryas integrifolia), and cottongrass (Eriophorum vaginatum) — which Jakob focusses on in his studies.

Cottongrass grows in a mound-like form known as a tussock. Credit: Isla Myers-Smith.

Cottongrass grows very slowly. The average age of a tussock is 100–200 years old, reaching a size of around 50cm in width. Dormant over winter, the plants only grow in summer, but we don’t fully understand what signals they use to know when they should start growing again each spring. Jakob’s research projects aims to find the answer. He uses observations from 60 individual plants laboriously collected by local rangers over the last 15 years and combines them with drone imagery to understand whether the plants behave the same way across the landscape.

“We use drones because the Arctic is a vast area, and it’s difficult and expensive to survey,” said Jakob. “Modern drones are simple to operate; we can just programme them to fly back and forth across the tundra, mapping large areas by themselves. The technology is rapidly developing, improving scientific data quality and ease of handling. We currently have a collection of about 10 drones that we use. Some are fixed-wing aircrafts like a plane and others are multi-copters, a bit like the models people like to buy and use at home, only bigger!”
Shrubcopter—one of the drones used by Jakob. Credit: Isla Myers-Smith.
A drone-eye view of the cottongrass tussocks. Credit: Jakob Assmann.

As they fly, the drones take images in the red and near-infrared spectrum at a 5 cm resolution. The presence of chlorophyll in plants affects how red and near-infrared wavelengths are reflected off their structure, and this makes it possible to distinguish different plant communities; such as an area that’s dominated by shrubs or one with sparse grass cover. The red and near-infrared spectrum is also excellent for differentiating between water, snow, soil, rocks and vegetation, explained Jakob.

Each pixel in this multispectral image represents 5 cm on the ground. Green to yellow pixels indicate the presence of productive plant material and the big green-yellow patches are cottongrass tussocks.

At the end of each flight, Jakob downloads the images and uses a programme to stitch them together to create a 3D map of the landscape. By estimating how much active plant material there is in each pixel, you can infer how productive the plants are. With the help of these images, Jakob is investigating how the productivity of the landscape changes across the growing season and over the years; which parts of the landscape are more productive and why; and which parts of the landscape are getting more productive (or less). Information of this kind can help us understand the impact of environmental change on plant communities.

Jakob’s also looking at whether or not data collected on foot and by hand with a ruler agrees with drone and satellite imagery. He’s learning what minimum pixel size is needed to measure changes in plant productivity, so we can use satellite images to fill data gaps.

From the 1970s onwards, scientists have studied the Arctic using satellite imagery with a spatial resolution of 8 kms, a huge contrast to the capabilities of today’s satellites which take images at scale of 1–10 meters. Despite their low resolution, these images have captured the greening of the Arctic and are an important record of the region’s seasonal and long-term changes.

“I love watching NASA’s animations of satellite images that show the cyclical change, it’s like watching the planet breath,” said Jakob. “It’s too soon for the high-resolution satellite images to reveal anything new about long-term change in the Arctic but we’re excited that this level of imagery is now available.”

Technology helps us study our environment in new, exciting ways. And for curious minds like Jakob’s, it presents an opportunity to uncover the secret life of plants. As we learn more about the cues and signals that affect plant productivity, we can understand better how plant communities respond to rapid environmental changes and what impact a warmer climate might have.

The desire to understand the world around us is an inherently human quality but with the aid of technology we are learning faster than ever before. Empowered by new data and knowledge we can make better choices for our planet and continue watching it breath.

I’d like to say a huge thank you to Jakob for talking to me about his work and for sharing his amazing pictures with us!


Recommended reading:

For more information on the greening of the Arctic, read the IPCC Climate Change 2014 Synthesis Report Summary for Policymakers, page 6 onwards.

Learn more about Team Shrub and their research by following them on Twitter or Facebook, or visiting their website.