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NASA satellite imagery monitors mangroves in Mumbai

NASA has released high-resolution Landsat satellite imagery of the mangroves around Mumbai — the thriving financial center of India housing 20 million people — that helps in monitoring mangroves and clearly identifying the damage due to indiscriminate, haphazard urban development and rapid expansion of the densely populated metropolis in the last few decades, as well as the few areas where mangrove growth has increased.

The NASA Landsat images are centered on the Thane creek, one of the main waterways flowing through Mumbai and a recently declared Flamingo sanctuary, which has more than 59 km (23 miles) of mangroves.

 Landsat imagery monitoring mangroves

monitoring mangroves in Mumbai
Landsat satellite imagery captured in 1988. Courtesy: NASA
monitoring mangroves in Mumbai
Landsat satellite imagery captured in 2017. Courtesy: NASA

The NASA imagery provides a very clear and holistic picture that will help in understanding the extent of destruction and thereby curtailing further damage.

The two images are juxtaposed together. One was captured in 1988 and the other in 2017; the difference of more than two-and-half decades between the pictures enables very precise and comprehensive observation and data analysis. In the images, the dark green areas along the creek show the mangrove forests. The buildings and adjoining roads are shown in white color. Both the images were captured during high tides.

Between 1998 and 2017, a lot of mangroves were encroached by large-scale construction and development projects due to massive population and the soaring demand for new residential areas. For instance, the Deonar landfill expanded significantly and new residential and commercial complexes that sprang up along the northern edge of the Thane creek. This year alone 80 cases of mangrove destruction were reported in Mumbai and none of those involved have been booked under the law.

The images also highlight that over the years sedimentation has narrowed the channel of the creek and lead to mangroves spreading over the center, which is a good trend and would lead to an increase in mangrove cover, as per some researchers. But, at the same time, other scientists have observed the alarming trend of decline in mangrove cover.

Monitoring mangroves for preservation

Mumbai has total 5,800 hectares of mangrove cover, of which 4,000 hectares lie in government-owned land and 1,800 hectares in private areas.

Most of the waterbodies in and around Mumbai are surrounded by mangroves, which are short, shrubby trees growing in swampy areas and marshlands. Mangroves not only host a variety of flora and fauna but also help protect the shoreline by reducing soil erosion, providing stand protection from waves and offering a natural barrier against inundation. Destruction of mangroves leads to ecological imbalances, environmental hazards and increases the risk of flooding.

In a bid to protect and preserve mangroves in Mumbai, the state government has decided to monitor them using real-time satellite images. The mangrove cell of the Indian state of Maharashtra has commissioned a research project to track mangroves and send the report to the forest department on a monthly basis. In November 2017, the Maharashtra Forest Department signed an agreement with the Indian Space Research Organization (ISRO) for using satellite imagery to monitor mangroves in the state. Along with it, it has been decided to cordon the mangroves by a 10-foot wall around the coastline.