Walter Gehring (1939–2014)

and time. However, it’s not all about machines taking over from field workers. Technology can also help to get more people involved with field work in ecology and conservation. The Earthwatch Institute (www.earthwatch.org), for instance, supports a project called My Tree Tracker, based on a smartphone app encouraging volunteers to keep an eye on the growth and health of the trees in their cities. Just by recording very simple datapoints including the location, species, and circumference of trees in their neighbourhood, people can make a valuable contribution to ecological studies characterising the ‘urban forest’, which in turn helps to make modern cities a healthier and friendlier environment. In 2012 and 2013 Earthwatch engaged over 300 volunteers to measure over 5,000 trees in four US cities, including Cambridge (Massachusetts), San Francisco, Chicago, and Atlanta, and the organisation is aiming to expand the project further. Overall, from simple free apps and recycled smartphones through to drones and satellites, modern technology offers many tools that can help ecologists and conservationists with their work. As Nathalie Pettorelli concludes: “Satellite remote sensing, camera traps, microphone arrays, guided drones, Doppler radar: these are all becoming central to our ability to understand and manage our natural world”.