Whether human-induced activities could change the gradient pattern of coastal land use along the sea-land direction: a case study in Manila Bay, Philippines

Increasing intense human activities have largely changed the coastal landscape and caused many environmental issues. However, whether human-induced activities could change the coastal land use gradient pattern, an important coastal zonal characteristic along the sea-land direction, remains unclear. Manila Bay was selected as the study area in this work. According to the distance of the land use and land cover (LULC) to the coastline, we clustered the typical coastal land use sequence patterns (CLUSPs) along the sea-land direction between 1988 and 2016 in Manila Bay and found the following. (1) Four typical CLUSPs, including the natural CLUSP dominated by forest land and grassland, the agricultural CLUSP dominated by dry farm and paddy field, the urbanised CLUSP dominated by construction land and the fishery CLUSP dominated by fishing farm, were mined in 1988. Three typical CLUSPs (a natural CLUSP, an intermediate CLUSP between the agricultural and urbanised CLUSPs, and a fishery CLUSP) were mined in 2016. (2) Affected by the dominant LULC, these typical CLUSPs showed a regular spatial pattern along the sea-land direction. For example, the typical natural CLUSP showed a landward pattern due to the long distance between the forest land and grassland and the coastline. (3) However, influenced by urban and aquaculture expansion, the land intensification of the CLUSP exhibited an obvious increase and caused the decrease of the CLUSP diversity from 1988 to 2016. The increase in the area of LULC coverage showed no obvious correlation with its distance from the coastline (DFC), but the net increase rate of LULC coverage had a significant negative correlation with the DFC. Therefore, human-induced activities have a large impact on the gradient pattern of coastal land use along the sea-land direction.