With the help of Dr. Chandra Giri of the US Geological Survey, we have begun to map the mangrove die-off in the Marls. Using Landsat images, or high resolution satellite images, and principles based on the optic properties of healthy vegetation we can calculate an index called the Normalized Difference Vegetation Index, or NDVI. NDVI ranges from -1 to 1 and the basic idea is that the denser the live vegetation the closer the value is to 1. Because Landsat images are available from 1972 on we can go back in time and calculate the amount of healthy mangroves in the Marls. By doing so we will be able to gain a better understanding of when the current die-off started, how mangrove health is related to big events such as hurricanes, and monitor the rate at which the die-off is expanding.
In the above image you can see a Landsat image of the Marls on the left. The two images on the right are of the area enclosed by the box in the image on the left, this is an area of known mangrove die-off where our lab has begun conducting experiments. In the two images on the right red coloration indicates an NDVI value closer to -1 (or unvegetated areas) while live vegetation with an NDVI value closer to 1 appears green. As you can see, there has been an extensive reduction in the amount of live vegetation in this area over the past 15 years.
The images above are just a starting point and we look forward to delving into this further and sharing our findings!