Hydrologically speaking, the most ideal land use is that of closed forest stands represented by dark green colors in Figure 1. Unfortunately, only the northeastern part of Bukidnon and the eastern part of Lanao del Sur (as of 2003) have closed forest covers. What I mean of hydrologically ideal situation is the capacity of a certain land cover type to retain or delay runoff caused by rains. Once these closed forest stands are disturbed its retention capacity is diminished significantly (in the order of 30 to 50%). These are the areas represented by light green or the open forest stands in Figure 1. Even reforestation cannot revert the hydrological capacity back to its original capacity. Virgin forest once lost has no hope for recovery. Closed forests have an ecosystem structure perfected through centuries of evolution. The hydrological capacity is not only about trees but also include the species assembly underneath the canopy. Thus, reforestation is better if done in such a way that shrubs, grasses, bushes are included in the program not just trees. In biosystems engineering, we call it biomimicry.
Similar in hydrological capacity to open forest is the wooded grasslands represented by the peach color. Though not as effective as the closed forest, this land cover type is better than the cultivated annual crops cover represented by yellow colors. It is worthy to note that wooded grasslands, closed and open forests in the eastern portion of Bukidnon have made the hydrology of Davao river stable and tamer. But once the agricultural activities in the Cabanglasan and San Fernando in Bukidnon intensifies, it will be a nightmare for Davao City. I heard that a road is being constructed in the areas that would connect Bukidnon with Davao del Norte. This would mean intensified economic activities in this Bukidnon territory. And if Davao City will open their northern frontier to economic activities (conventional agriculture, etc.), it would be a disaster waiting to happen.
The prevalence of annual crops (yellow areas) has disabled ecosystem services that Bukidnon provides in terms of hydrological regulation (flood delay, and water during drought). This makes the receiving provinces of North Cotabato, Maguindanao and CDO at the mercy of Bukidnon waters (from different watersheds!). This is demonstrated by the perennial problem of flooding in Maguindanao and Cotabato City. Unfortunately, we tried to solve Cotabato floods by controlling the water lilies. Personally, I believe it is better to start seriously looking at the land use practices in the heart of Mindanao. The erratic nature of weather patterns needs adaptive interventions that transcends boundaries and academic disciplines.
Here are some weak points, I believe we need to address:
1) We need to review the different land use plans of the municipalities (CLUP). Does it conform to the whole river basin hydrodynamics? Does the projected land use take into account the possible consequences it may impose on our hydrology? Several accounts would point to CLUPs being a "copy and paste" plans. This is where the LGUs need to craft their respective land use plans that conforms with the ecological dynamics beyond their territorial limits.
2) There is a need to delienate the final limits of forest lands and those alienable and disposable. It can be gleaned in Figure 1 that a lot of forestlands were already cultivated. For example, in Bukidnon, 491,579 hectares were classified as forestlands but only about 170,000 hectares are with forest covers with over 100,000 hectares already open.
3) DENR, DAR, and DA should work hand in hand in developing upland agriculture that focusses on land and water conservation. DA and DAR refuse to work on forestlands eventhough agricultural activities are evident simply because it is within the domain of DENR. DENR are "tree - oriented" and may be not technically conversant with appropriate agricultural technologies that farmers need. On the other hand, agricultural professional are "plantation-oriented" and may not be technically equipped in dealing with smallholder sloping agriculture. If only DENR, DAR, and DA creates a liason office that deals with rigors of upland and sloping agriculture or agroforestry. I think it is no longer possible to reforest the whole 491,579 forestlands but agricultural and environmental agencies can work together in developing economic activities in the uplands that can maintain vital ecosystem water resources services.
4) Built up areas (red colors) should be redesigned that considers storm water regulation. Our preference to pavements in real property development makes a concrete jungle that has the worst hydrological capacity. This is demonstrated by Typhoon Ondoy. Rainwater harvesting and stormwater retention facilities can be embedded in urban structures.
5) Enforce forestry laws to maintain the integrity of the last remaining closed forest. I guess a total log ban is in proper. A log ban for both legal and illegal logging of natural forests. In order to supply our timber needs, tree planting should be encouraged in non-critical parts of the watersheds.
6) Downstream provinces and cities need to reconsider their "dikes and dams" mentality as flood control. Engineering designs are usually based on hydrological analysis. Unfortunately, some of our historical data (if there is such data existing for specific locality) do not capture uncertainties brought about by climate change and the faster land use transitions brought by human activities upstreams. And so our usual dam and dikes solution may not work in the long run. There should be plan B - and that is adaptation and mitigation. What I learned from Dutch water engineering is that water is difficult to control and so they make do of floating structures (bridges, houses, etc.). Instead of relying much on dikes, they make more "room for rivers" and "space for waters". They keep on studying their situation and propose solutions beyond engineering realms.
There is a need to rehabilitate our river basins. Let the heart of Mindanao pump life again. A transboundary natural resources management is imperative that addresses the biophysical and social dynamics of the river basins. A participative and adaptive mechanism that connects stakeholders from different spatial scales and technical backgrounds. Let us remember that water knows no boundary.