One fine example is Bohol's manmade forest. This forest of the non-native mahogany (Swietenia macrophylla) is considered one of the province's major tourist attractions. It is a source of pride as it is a living proof of Bohol's accomplished environmental project. It was in 1968 when the local government asked students to plant the mahogany seedlings to reforest a portion of Billar town. Forty years after, the seedlings have grown to considerable size, forming a forest dominated by a single introduced species.
I remembered uttering the phrase 'parang wala ka sa Pilipinas' (as if you are not in the Philippines) when I first caught glance of the manmade forest. Now I understand why. It reminded me of a temperate zone woodlands where single or only a few species dominate because of low biodiversity. The usual Philippine rainforest would have a varied selection of trees as it has high biodiversity. But because the government is still maintaining the dominance of the mahogany, the native species are given less chance to repopulate the area. Fallen mahoganies are replaced with mahogany seedlings rather than letting the native species get a foothold and reestablish themselves.
But upon closer look, the native species are undoubtedly trying their best to reemerge. Native Pandanus species seedlings are growing under the shade of the tall mahoganies. Celtis seedlings are waiting for their chance to get their share of sunlight, which is hogged by the tall exotics. Osmoxylons are trying their very best to survive, trying to get whatever share of filtered light they could steal from the thick canopy. The natives are there patiently waiting.
If the Bohol people only planted native species in 1968, the manmade forest would have boasted large specimens of dipterocarps or perhaps kamagong by now and not these introduced mahoganies. Probably sometime in the future the locals would grow tired of maintaining the dominance of this exotic species. Hopefully when it happens, the dipteros and the natives like kalingag liitan, binunga, molave, antipolo and a selection of others would reclaim the land and repopulate. The great diversity of large native species would have been a better spectacle to see than the monotonous tall mahogany trunks visible in the manmade forest.