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SMART RESILIENT AIRPORT
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Turf Management To Reduce Bird Hazard In Airports
Introduction
Turf management is one of the most important and continuous efforts put by airport authorities to keep the area clean, reduce the bird activity and increase visibility to pilots/air traffic control tower. It is estimated that in India alone, more than 50 types of grasses grow in airports. In one of the studies conducted at Jamnagar airport, we recorded as many as 38 species of grasses.
Grasses on runway shoulders can be seasonal or perennial. A seasonal grass grows quickly during Monsoon, bloom and set seeds before drying up in winter. Such grasses pose fire hazards in many airports during pre-monsoon season if not managed properly. Scientific research by Bombay Natural History Society (BNHS), India in the year 2000 noted that our airports support a contiguous, undisturbed and protected grassland habitat – one of the last few remaining ecosystems in India. Grassland habitats outside airports
largely have vanished either to agriculture or for township developments. The study went on further to note that due to shrinking habitats outside, more and more birds have found refuge in airport grasslands. The share of small bird strikes has increased (from 5% in 1980s to > 30% in 2010) – leading to increased number of engine withdrawals. According to International Bird Strike Committee (IBSC), 60% of the bird strikes happen below 30m where, grass management becomes an important aspect.”
Bird dependence on turf
I have recorded more than 67 species of birds that directly or indirectly are dependent on grass cover on runway shoulders. Birds are attracted to turf mainly for four reasons: feeding, breeding, resting and roosting. Grasses provide food in the form of seeds, young shoots, insects and midges on which birds thrive. Grass blades, sticks and roots are collected by birds for building nests and some birds like Larks, Pipits and Sparrow Larks build their nests at the base of the grass clumps. Tall grasses of more than 75cm are used by some warblers (Zitting Cisticola – in picture) to build nests in Monsoon. On a hot afternoon, one can see many small birds resting at the base of the grasses. Short grasses of 6 inches height are preferred by Olive-backed Pipits in North-Eastern airports for roosting in the night (spending the night). In mainland airports, short grasses are used by Paddyfield Pipits, Oriental Skylarks, and Crested Larks to roost in the night. Such birds do get disturbed in the night and become a problem to aircraft while shifting their roosts from one clump to another.
The hard fact is, at all heights of grasses, one or the other kind of birds is attracted. It is impossible to eliminate the bird attraction to turf on runway shoulder. On the contrary, elimination of the grasses in itself is also not the solution. Barren patches on the turf are preferred by Ashy-crowned Sparrow Larks and Sandgrouses for roosting and are problematic in many Indian airports during night.
Indian Scenario
In 1982-88, Bombay Natural History Society (BNHS) recommended Dhub grass (Cynodon dactylon in picture) for most airports of India. The project was tried at many airports without much success as the recommendation was silent on soil, water and climatic requirements of Dhub. Despite multiple efforts as recently in 2009, the grass did not establish on runway shoulders.
Many airports in India have opted for Kikuyu grass (Pennesetum clandestinum) on the runway sides. The grass is a spreading, forms a dense turf and needs good management. There has been a mixed response to the survival rate and spread of this grass at IGI airport, Delhi, Bangalore International Airport (BIAL) and GMR Rajiv Gandhi Hyderabad International Airport (GHIAL). Runway environment cannot be made unattractive to birds by maintaining a uniform stand of grass throughout the year without any regard to the type of bird that inhabits the airport.
There is an advantage in retaining local grasses in the airports as it helps us manage birds easily and in an innovative way. One good example is complete reduction of Greater Short-toed Larks during winter months at Bidar airport. The airport authorities followed the recommendations of the expert studies and let the grass grow to 75cm for three months in winter. It has been since 2009, there is no Lark problem at the airport whereas, millions of them could be found just outside the boundaries of airport!
The requirement
The most logical way for turf management in airports could be summarized in following few steps:
1. Know your grasses in airport. There may be a few good species that help in reducing attraction of birds to airport.
2. Map the distribution pattern of existing species of grasses. Most grasses occur either in single or mix of two to five species in a patch (see picture)
3. Test the soil nutrient availability
4. Test the water quality
5. Consider weather factors
6. Determine the bird activity associated with grasses
7. Select beneficial grasses to be retained
8. Identify the problematic species that are attractive to birds (produces seeds prolifically, susceptible to insect pests, provides nesting materials and sites to birds)
9. Logical calculation of grass height to be maintained in each season with respect to birds you have.
10. Develop a 12 month calendar for grass maintenance.
Once developed, the program helps in micro-managing grass maintenance to reduce bird activity. One can target spraying of insecticides/weedicides at a particular patch (instead of entire airport). Beneficial grasses can be left untouched or encouraged to grow. Grass management being done at Jamnagar airport based on such studies is helping airport authorities to save (cost) on manpower, insecticide/weedicides while reducing the bird attraction next to runway.
Conclusion
Since it is impossible to completely avoid birds whether an airport has grass or not, the model should consider using local beneficial grasses and variation in grass height in different seasons for managing birds. Flexible height based management helps in minimizing the cost of operations while maximizing the benefit. Minimum possible reduction in attraction of birds to turf, an airport can achieve, is only possible by going in for logical grass management and not by having a uniform grass stretch.
Comtributed by - SS Mahesh, CEO, Via Life Sciences, Bengaluru
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