The mangrove planting in San Remigio was started by a community organization called TUFFA which is looking into planting mangroves where mangroves were destroyed by typhoon Yolanda, and cut down for wooden resources. They're doing this because mangroves are known as "Buffer Zones" and during a typhoon there is something called a Water Surge (a coastal flood or tsunami-like phenomenon of rising water commonly associated with low pressure weather systems such as tropical cyclones and typhoons.) These Buffer Zones reduce the impact of the Water Surges to the community. This is why Mangroves are vital to the community and the San Rem trip for the past years have been planting mangroves. This year we managed to plant 500 mangroves that day and hopefully our work will benefit the community if a typhoon hits them.
When planting mangroves there are specific needs of the mangrove. One of them is that the mangroves must be a certain distance apart in order to grow, if they are too close then the mangroves will be competing for nutrition and water, therefore only one of the two will survive. If they are too far apart then they are not utilizing all the space there is. Another is that when they are planted they can't be too far under the ground as their roots will drown and if their too high they won't get enough water and will dry out.
Above is an example of how mangroves work and how they reduce Water Surges.