Airports can impact biodiversity in a number of ways, including loss or degradation of habitats when airports and airfields expand, deterring or controlling wildlife for operational reasons, and through the effects of light and noise pollution on some species. A list of biodiversity indicators is published and maintained by the Government.
Bird populations can both harm and be harmed by aircraft. In particular, large flocking birds, especially geese, are seen as a threat to the safety of aircraft, as exemplified by the well-documented case in 2009 when a plane was forced to make an emergency landing in New York’s Hudson River after a flock of birds collided with both its engines. In the UK, over 2000 bird strikes are recorded annually. The CAA advises that steps should be considered to minimise bird populations as far as ten miles away from airports. Reducing the attractiveness of surrounding areas to large birds – for example by removing trees or other nesting habitat, or using noise and flare guns – can in turn impinge on other wildlife populations. The law allows Natural England to issue licences to airports to kill a range of bird species within an area 13 kilometres from the airport boundary, including many species of geese and gulls, if there is danger to the safety of plane flights.
Biodiversity impacts are usually addressed in the context of airport planning applications, and environmental assessments should identify sensitive habitats, any risks, and appropriate mitigation. Examples of mitigation include re-creation of habitats elsewhere to provide a home for flora and fauna, or the diversion of watercourses. In some cases, the significance of likely biodiversity impacts can delay or stop expansion. In the 1990s, planning permission for a development at Lydd Airport was delayed while investigations took place into the impact of aircraft noise on the breeding success of birds at the adjacent internationally protected wetlands. Birds and other animals can be very sensitive to aircraft noise. US research showed that while some bird species took no notice, others could be startled and some left the area permanently.