Protecting Europe's nature reserves using LIDAR

Scientists from the Vienna University of Technology (TU Wien) in Austria are developing a LIDAR remote sensing system to monitor Europe’s nature protection areas, which make up almost one fifth of the land space in the European Union.

The new instrument will be used to monitor areas according to EU regulations, which includes analysing the ecological condition of woodland, status of the habitat as well as human activity.

Simply declaring a region as a nature protection area is not enough, regular monitoring of its ecological condition is also necessary. ‘The rules of the Natura 2000 network of nature protection areas request the evaluation of the conservation status of protected region at least every six years,’ said Professor Norbert Pfeifer from TU Wien. ‘This can only be achieved with the help of remote sensing.’

The classification software developed by the TU Wien team is able to recognise a broad range of parameters similar to what would be collected during an inspection carried out by ecologists, which includes recognising different types of vegetation as well as human activity such as vehicle tracks.

Therefore, the data complies with EU regulations and can directly be compared to older data.

‘When people process remote sensing data for ecological monitoring, they usually focus on very specific parameters which are easy to derive,’ Pfeifer explained. ‘Our approach is quite different. We use the data to calculate precisely the same parameters as they are collected in a site inspection by human ecologists.’

The LIDAR device works by firing short laser pulses to the ground, where information on the status of the habitat can be deduced from the reflected light signals using elaborate computer algorithms.

Planes fly at an altitude of 500 to 2,000 metres, scanning a strip 300 to 800 metres wide. About ten points per square meter are sampled using an infrared laser pulsing half a million times a second. The pulses are reflected and return to the plane, which means the exact distance between the plane and the ground can then be calculated in order to create a detailed three-dimensional map of the landscape.

Lower layers of the vegetation can also be surveyed, as some of the infrared laser light can penetrate through the tree tops, which is important in determining whether the woodland is ecologically healthy.

The newly developed computer algorithms were tested in the nature protection area of Ágota-puszta, Püspökladány in Hungary, which consists of a mosaic of salt meadows, loess grasslands and marsh areas. Part of the field data collected during this test was used to adjust the algorithms and validate the method. ‘We achieved an agreement of 80 to 90 per cent between our data and on-site observations,’ noted Pfeifer. ‘This is a huge success. It is about the same level of agreement that would be expected if two different people assess the same region.’

‘This study is a major step forward in closing the gap between the remote sensing and conservation ecology communities,’ added András Zlinszky, from the Centre for Ecological Research in Hungary. ‘We have shown that it is possible to monitor Natura 2000 conservation status by remote sensing, exactly following the rules laid out by the local ecology experts.’

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