sentences:  Marikina River used to be an important transport route during the Spanish colonial era, but its importance as a transport route diminished when the Philippines' national highway system became more established.The resulting lack of river boat traffic and the deforestation of the upland areas in what is now the Upper Marikina River Basin Protected Landscape contributed to the river's siltation, further reducing its value as a transport route.Due to negligence and industrial development, the river has become very polluted, an act which recent Marikina City administrations have attempted to address.