Posted in | News | Ecology

Mixed Forests Better Equipped to Handle Tsunami Waves, Study Shows

Coastal forests in Japan had predominantly been afforested with black pine (Pinus thunbergii), a shade-tolerant tree species that can withstand dry land ecosystems and harsh coastal environments. This afforestation initiative, dating back to the Edo period (1603~1867), aimed to mitigate the deleterious effects of robust winds and sand blowing. Subsequent to the Great East Japan Earthquake in 2011, interest shifted to the potential protective effects of coastal forests in reducing the destructive power of tsunamis.

The Great East Japan Earthquake tsunami damaged a total of 2,800 hectares (ha; 10,000 square meters) of coastal forest. While the damage was immense, the devastation provided an opportunity to study which coastal forests withstood the tsunami impact and why some forests fared better than others. The forests can only mitigate tsunami effects if trees remain intact during the tsunami. Recently, scientists from Yokohama National University discovered that coastal forests that contained mixed tree species bore the tsunami forces better and with less damage than monoculture forests made up exclusively of black pine.

The research team published their findings in the 16 October issue of Natural Hazards.

"Prior studies have established that coastal forests decrease the hydrodynamic forces exerted by tsunami on structures and alter inland debris dispersion based on the density and size structure of trees. However, limited attention has been devoted to exploring the role of species diversity in coastal forests. We revealed that mixed coastal forests with black pine exhibited a diminished vulnerability to tsunami impacts when contrasted with monoculture forests," said Yuki Iwachido, first author of the study paper and assistant professor at Yokohama National University.

The research team determined the effects of species diversity in coastal forests by analyzing satellite images and aerial photographs of coastal forests before and after the Great East Japan Earthquake tsunami on 11 March 2011. The degree of damage between forests that contained only black pine trees was compared to the damage experienced in mixed species forests made up of black pine and other broad-leaved trees.

The researchers hypothesize that mixed forests are less susceptible to tsunami damage because the root morphologies of different tree species utilize more soil space and resources than a single species of tree. In theory, this could enhance aboveground tree growth and overall stability of the mixed species forests. One limitation of the research was that the scientists couldn't compare their results to a monoculture of broad-leaved trees and therefore could not remove the impact of coniferous trees.

The study also found a benefit in complex tree planting arrangements compared to simple arrangements. Analysis of the visual impact of the Great East Japan Earthquake tsunami suggests that forests with complex spatial structures were more able to withstand tsunami forces.

The research team acknowledges that more studies are required to better understand the capacity of coastal forest tsunami protection and how to maximize its safeguarding effect. "This study primarily focused on analyzing only damage patterns to coastal forests caused by tsunami impacts utilizing satellite images. There is a pressing need to elucidate the mechanisms by which mixed coastal forests alleviate the impacts of tsunamis," said Takehiro Sasaki, senior author of the study paper and the professor at Yokohama National University.

Minori Kaneko from the Graduate School of Environment and Information Sciences at Yokohama National University in Yokohama, Japan also contributed to the research study.

This work was financially supported by a Fostering Joint International Research A grant (no. 19KK0393) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.

Source: https://www.ynu.ac.jp/english/

Tell Us What You Think

Do you have a review, update or anything you would like to add to this news story?

Leave your feedback
Your comment type
Submit
Azthena logo

AZoM.com powered by Azthena AI

Your AI Assistant finding answers from trusted AZoM content

Your AI Powered Scientific Assistant

Hi, I'm Azthena, you can trust me to find commercial scientific answers from AZoNetwork.com.

A few things you need to know before we start. Please read and accept to continue.

  • Use of “Azthena” is subject to the terms and conditions of use as set out by OpenAI.
  • Content provided on any AZoNetwork sites are subject to the site Terms & Conditions and Privacy Policy.
  • Large Language Models can make mistakes. Consider checking important information.

Great. Ask your question.

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.