Drones: the pros and cons for community-based monitoring
This webpage explores the advantages and disadvantages of drones for community-based forest monitoring using information from a variety of sources, given in links throughout and in the related links at the end of the page. It draws particularly from this paper of 2014 by Jaime Paneque-Gálvez et al, who kindly reviewed this page.
Many forest communities occupy large, sparsely populated areas, so the ground surveys carried out during conventional community-based monitoring can be time consuming, expensive, dangerous and logistically difficult. Furthermore, while ground surveys can yield a huge amount of data on biodiversity, they are less efficient at collecting information on irregular and subtle processes of forest degradation, and it can take time for monitors to reach and assess deforested areas.
As of the start of 2016, monitoring with drones is in its infancy. Consistent and conclusive results are yet to be obtained, though some early results have been encouraging.
If used appropriately and combined with ground surveys and local knowledge, drones can constitute a valuable tool in monitoring, researching and mapping forests, as well as a deterrent to those who encroach on protected areas and indigenous lands (such as illegal poachers, cattle ranchers, loggers and miners). They can combine low cost, speed and an aerial perspective, with sophisticated sensory technology to provide extensive and detailed data on forests in a short period of time.
Drones are being used in several initiatives to deter illegal intrusions, to map community land, to detect illegal logging, to assess fire damage and – usually in more open landscapes such as savannahs – for surveillance against poaching of biodiversity. For example, this initiative shows how drone use is taking off among indigenous communities in Panama, while in Guyana indigenous people also found that using drones can make monitoring easier and reduces risks. However, other projects report issues, such as data accuracy. While drones are an exciting new technology with many potential uses for conservation, they are not a panacea to the complex and daunting issues facing forest communities, and forests themselves.
Before initiating any community-based forest monitoring using drones, communities and partners should be sure to understand and discuss the advantages and disadvantages, as described below. Particular attention should be paid to social issues, free, prior informed consent (FPIC), data sharing, and questions to make sure that the drone fits its specific purpose.
Advantages for particular groups
Although listed by actor, many of the advantages and disadvantages below are relevant to many groups.
- Many forest communities do not have official government recognition for their traditional lands. Images from drone surveys can be used to create detailed maps of forest cover, agricultural areas and communities, which can strengthen communities’ proposals for land titles.
- The forest survey data from drones can provide a range of objective evidence that communities can use in negotiations with public agencies and other land users (such as forestry companies). Communities can push governments to incorporate this into environmental policymaking and spatial planning, and use drone images or videos as a powerful tool for wider communication on their achievements and the threats they face.
- Drones facilitate the detection and assessment of illegal deforestation, mining, fires and oil spills that threaten the livelihoods of forest communities. They can also identify camps, trails or boats of intruders such as illegal hunters, miners, loggers or fishermen, gathering evidence of illegal forest use without running the risk of intercepting criminals directly.
- Drone images can complement data from ground surveys to create estimations of forest carbon content, so could be a valuable tool for communities who wish to participate in and benefit from REDD+.
- Drones can collect detailed and accurate information on otherwise inaccessible areas, increasing community knowledge of the state of their land.
- Accessing high-resolution images from satellites can be costly and timeconsuming; drones can provide data direct to communities more quickly and cheaply.
For governments and partner organisations
- Community-based forest monitoring using drones decentralises forest monitoring, putting less pressure on the time and budgets of governmental departments. If used correctly drones can enhance local knowledge of forests, contributing to effective forest management. Research shows that locally collected data can usefully complement remote sensing data; some of these findings could be applicable to combining drone images with participatory monitoring.
- Drones may be more cost-effective for donors than other remote sensing technologies. They are also increasingly easy to use, reducing the costs of training, and can be shared between several communities.
- Drones can help identify forest types, making it easier to select plots for more detailed on-the-ground surveys (as well as map these plots accurately). Drones can also focus on areas identified during participatory mapping processes. This reduces the number of plots and ground surveys that are needed.
- Drone imagery and data can be used to verify forest cover and give assurance to investors who are making REDD+ payments to communities.
Disadvantages for particular groups
For communities and partner organisations
- Drone use could lead to conflict and accusations of spying. Most forest communities have few reasons to trust organisations that express a desire to survey their land, and some cultures could view drone technology as an external imposition. If a monitoring operation is more attuned to the objectives of an external organisation than the needs of a forest community, it is likely to lead to tensions between the community and the organisation.
- There could be risks that partner organisations could see drones as a mapping shortcut to replace participatory mapping and monitoring processes, that typically include indepth discussions with various sections of the community, and face-to-face conversations during surveys. This could lose the many benefits associated with these processes (as described throughout this website).
- There are also ethical issues relating to privacy and gender, if one group has the technology to observe another (whether one village able to fly drones over a neighbour, or men having greater access to surveillance technology and images than women).
- The legislation around drone flights or aerial surveys over forest areas and indigenous lands can be unclear. Conditions for the use of drones need to be agreed between, for example, community members, public bodies and external facilitators.
- To address the points above, in-depth discussions before any drone monitoring are essential, to ensure that drones use is indeed what all members of the community want, and will further their objectives. Access and use of images should be openly discussed and agreed; communities should retain rights over data to reduce tension over data sharing. Drones should complement and support participatory mapping and monitoring, as part of a wider process of community empowerment. The fact that drones can be completely unfamiliar means that their function, purpose and likely flight times should be fully explained to all local communities to avoid spreading alarm.
- Community-based forest monitoring with drones is dependent on training in drone maintenance, piloting and programming. Drone technology is unlikely to be familiar to local people, while data processing and geospatial analysis will need support from a partner organisation. So drone monitoring relies on external assistance (although the extent of this assistance may diminish as drones get cheaper and more user-friendly).
- Illegal loggers, poachers, ranchers, narcotraffickers or drug producers in forests might react violently to drone surveillance, either shooting down the drone or threatening community monitors, community members or external facilitators.
- Drones are by no means a panacea, and may not be effective in monitoring very large areas. The technology is not designed to monitor the same issues as ground surveys (such as soil carbon, or the impacts of illegal hunting on biodiversity).
- As drone use becomes more common, regulations are increasingly necessary. As governments develop drone legislation, they face the challenge of providing legal clarity and addressing potential conflicts of interest (for example, communities may wish to use drones to monitor areas used by extractive industries or agri-business, such as palm oil plantations). Controversies over drone use could require intervention by public agencies.
- Public bodies may be called on to resolve social issues and potential conflicts, described above.
Reduced operational cost and time
Drones can gather extensive data on an area of forest in a short period of time and at a low cost. It is relatively easy to launch drones on demand and to repeat surveys to capture change over time. This reduces the time needed for monitoring compared to regular ground surveys, so less time is lost from livelihood activities, such as farming.
Drone flights can be pre-programmed, and communities can potentially use automated or semi-automated drones for monitoring with less training than with a fully manual system.
Detailed images and models
Small drones of the kind best suited to community-based forest monitoring usually fly at an altitude of around 50-300m. The photographs taken from this altitude are of a higher resolution than satellite imagery, with pixels sized a few centimetres rather than a few metres. The clarity of photographs means it can be possible to identify canopy gaps, forest degradation, tree height and regrowth – and LiDAR systems (Light Detection And Ranging, using lasers) generate detailed 3D models. Combined with ground surveys, such models can support estimations of forest biomass and carbon. However, LiDAR systems are unlikely to be accessible to forest communities for some time.
Ease of updating data
Once a community has a drone and knows how to use it, flights can be regularly undertaken at a low cost. Data can therefore be quickly, easily and cheaply kept up to date.
Immunity to cloud cover
Drones fly below the clouds, meaning reliable data can be collected in most weather conditions.
Rapid technical advances are likely
Drones are becoming easier to use, more durable and reliable and are increasingly marketed to those with little experience or training. Their cost is diminishing, while technical capabilities improve.
Limited carrying capability and area of survey
Small drones can only carry limited equipment. This puts constraints on quality of cameras (for still or video images) and also flight time, as small drones can only take small, light batteries.
Compared to conventional aerial photography or satellite imagery, drones cannot cover such large areas in a single flight. Areas larger than a few thousand hectares may not be suitable for drone mapping (depending on the type of drone, as discussed below).
Vulnerability to damage and rough weather
Fragile drones can crash, collide with trees, or get damaged in the unpredictable conditions of tropical forests. Although drones can fly beneath the clouds, any wind, rain, and fog can affect not only how often a drone can be operated, but also the accuracy of the information it collects.
Drones pitch, roll and yaw, which can have adverse consequences for the accuracy of the data they collect. Even in favourable weather conditions, drones can struggle to deliver accurately geo-referenced data. The images from a drone may need ground truthing to verify what is happening in areas of interest identified by the drone.
The small cameras carried by drones take multiple images that need to be stitched together by programs such as Pix4Dmapper to make a cohesive map. The processing power such programmes require is rarely available in isolated forest communities.
Repairing and maintaining drones often requires specific parts. Delivering parts to remote forest regions will take time and money, and even with the right tools and parts, repairs can be difficult as highly technical skills are required.
Choosing a drone
For forest monitoring, drones should be affordable to communities and facilitators. The more expensive systems are more rugged, long lasting and produce better quality images: comparative costs and performance are given here. Control systems will need to be simple, in order to facilitate training and use, and durable, as the drones will be operated in remote areas in which spare parts will be difficult to come by. Buying a drone kit may be a suitable approach: these are comparatively cheap, and building a drone is a reliable way to learn how it works. There are free online resources sharing knowledge on how to build drones. This knowledge is also useful if the drone is damaged. Drones should be capable of covering an extensive range at altitudes between 50m and 300m – the optimum altitudes for high-resolution imagery.
Rotary drones have a short range (generally around 3km) and low endurance (generally around 30 minutes) as they require a lot of power, but have small batteries. Surveying a large area of forest with a rotary drone would entail multiple expeditions to a patchwork of areas, increasing operational time and cost. While this makes rotary drones unsuitable for monitoring large areas, they may be useful for short, localised surveying missions. Rotary drones are easy to fly and highly manoeuvrable; they can fly vertically and horizontally at a range of altitudes, and they can hover. This makes them well adapted to missions that require refined, detailed images. Rotary drones have the key advantage of vertical takeoff, so they do not need a landing strip.
Rotary drones are mechanically complex, so they are more likely to malfunction and more difficult and costly to repair than fixed-wing drones.
Fixed-wing drones are more aerodynamic than rotary drones, so they can glide, reducing their dependence on energy from their small batteries. They can fly faster for longer, increasing the range of each flight. This means they can cover a large area of forest in a single flight, reducing the time and cost of data collection.
Fixed-wing drones are also more simply designed than rotary drones, making them more durable and easier to fix if they break. Forest communities have been able to create improvised spare parts for fixed-wing drones. However, fixed-wing drones are challenging to fly (as shown by this video from Guyana), necessitating complex training, and require a landing strip to take off and land. In tropical forests, such an open clearing may not always be available.