What is it about?

Forest restoration is important to mitigate the effects of climate change. Lately, there is a growing need to expand this restoration to watersheds, i.e., areas that drain water into large water bodies. Its benefits include groundwater recharge and reduction of wildfires. But there is limited funding to achieve this, due to incomplete cost analyses of fixing watersheds. Pu‘u Wa‘awa‘a watershed in Hawai’i is home to some of the largest native dry forests. Sadly, this area is getting destroyed due to climate change induced wildfires, deforestation, and excess grazing by livestock. The authors of this study worked with the Pu‘u Wa‘awa‘a restoration managers to understand the benefits of their long term restoration plans. They measured the costs of achieving two goals—recharging groundwater and reducing the land's chances of catching fire. They found that restoring the entire watershed area is ideal to lower the risk of potential wildfires. This is because climate change has increased the chances of fires occurring in the area. Moreover, it has also decreased groundwater recharge by 50%. However, the type and location of restoration strongly affects its cost efficacy. The cost of reducing land flammability is greater at lower land levels than at higher levels. This is because of a lot of fountain grass growing in lower level areas. But the cost of recharging groundwater is lower at high level land, due to the ease of capturing rainwater.

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Why is it important?

Recharging groundwater requires a complete focus on high level ground, whereas reducing land flammability requires restoration of low level ground. There is little overlap of both areas, making it difficult to achieve both goals together. If managers have a low budget, they can benefit from focusing on one area at a time. But focusing more on high level areas can achieve both goals in the long run. This is because the land flammability will increase at higher levels due to the increasing dryness and likelihood of fires brought about by climate change. KEY TAKEAWAY: Pu‘u Wa‘awa‘a watershed is in urgent need of restoration. Focusing on high level areas in this region will allow the completion of both management goals of groundwater recharge and reduction of land flammability in a cost effective way.

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This page is a summary of: Estimating Cost-Effectiveness of Hawaiian Dry Forest Restoration Using Spatial Changes in Water Yield and Landscape Flammability Under Climate Change, Pacific Science, October 2017, Pacific Science, DOI: 10.2984/71.4.2.
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