Model shows human impact on threatened tree species and their adaptability to climate change
Potential distribution of endangered forest tree species in the Philippines is largely determined by anthropogenic variables, that is, human activity. These species also respond differently to climate change: some might benefit while others lose habitat.
Alfie Torres, a researcher with the World Agroforestry Centre Philippine program, has examined the effects of present and future climates on the geographical distribution of four threatened dipterocarp species belonging to the Philippine mahogany group—‘mayapis’ (Shorea palosapis), ‘tanguile’ (S. polysperma), ‘red lauan’ (S. negrosensis) and ‘white lauan’ (S. contorta)—in the Northern Sierra Madre Natural Park in the Philippines, one of the largest and most diverse protected areas in the country. Alfie developed species’ distribution models using a Maximum Entropy (Maxent) model, a machine algorithm based on the principle of maximum entropy. The study was part of the Biodiversity and Watersheds Improved for Stronger Economy and Ecosystem Resilience (B+WISER) Project, which is funded by USAID.
The study found that distribution of species was largely determined by anthropogenic (34.06%), climatic (33.68%), topographic (17.52%), vegetation-related (8.13%) and soil-related (6.61%) variables. On average, the top five predictors in the model were distance to roads, precipitation during the driest quarter, isothermality (evenness of temperature throughout the year), distance to rivers and land cover.
The present and future distribution of the four tree species in relation to changes in climate was also compared. The results showed that mayapis and tanguile would both benefit from future changes in climate as their suitable habitats would increase in range in the park. However, both red and white lauan would more likely experience a decline in the range of suitable habitats. This suggests that not all changes in climate might be destructive and that there could still be positive effects. This is discussed in more detail in a paper recently submitted for publication.
A previous modelling study by Kristine Garcia, Rodel Lasco, Amor Ines, Bradfield Lyon and Florencia Pulhin of the World Agroforestry Centre Philippines also used a Maxent model to suggest where threatened trees were likely to grow under a future climate.
Such models are important as they predict which places are suitable habitats for the threatened dipterocarp species and, thus, which areas should be conserved. They inform practitioners of how climate change might affect the distribution of these species and can help decision-makers plan better by including climate-change predictions into strategies. Conservation practitioners would benefit from learning how to more effectively use species’ distribution models.
The Northern Sierra Madre Natural Park in the northern Philippines is one of the largest and most diverse protected areas in the country. However, massive exploitation and illegal logging now poses a serious threat to biodiversity and rural livelihoods in the park. Climate change will also exacerbate the current conditions of the forest and biodiversity, hence, models help to understand what is happening and what can be done.
The Philippines is one of the megadiverse countries of the world, ranking fifth in diversity of plant species and housing 5% of the world’s flora. However, it is also a biodiversity hotspot of threatened forest trees.
This work is linked to the CGIAR Research Program on Forests, Trees and Agroforestry