01 JULY 2010 SUVA (PACNEWS) --- The Fiji based Secretariat for the Pacific Islands Geoscience Commission (SOPAC) has clarified claims made in a recent scientific publication that three island nations of Tuvalu, Kiribati and the Federated States of Micronesia were ‘growing and not sinking.’
This week in Suva, SOPAC director, Russell Howorth convened a special media briefing to explain what the real sciences on the ground say about the vulnerability of these low island atoll islands. Howorth strongly argued the article published in the journal Global and Planetary Change, “does not make sweeping conclusions that the vulnerability of our islands reducing, particularly with regard to the future impacts of sea level change.”
The article, peer reviewed by Arthur Webb of SOPAC said the study did not measure the vertical growth of the island surface nor does it suggest there is any change in the height of the islands.
“Since land height has not changed the vulnerability of each island to submergence due to sea-level rise is also unchanged and these low-lying atolls remain immediately and extremely vulnerable to inundation or sea water flooding, Webb argued in his peer review article. Webb said while the shoreline of these atolls appear to have responded well to sea level rise, it is not known how long this trend will continue or if this pattern is similar across the whole Pacific region.
“There are a range of other climate change stresses which may disrupt shoreline processes; e.g. sea surface temperature increase, ocean acidification, accelerating rates of sea-level rise and possible changes in storm frequency or intensity.
Any of these or a combination may result in overwhelming the present resilience of these shorelines and if such a “tipping point” is reached, these atoll shorelines could become rapidly erosive. He added that urban impacts such as beach mining or inappropriate coastal engineering can also cause intense erosion or disturbance.
His argument was supported by Howorth who said experiences have shown that traditional capacity has helped islands cope with their natural vulnerability. He used the example of the Nan Madol on the southeast corner of Pohnpei in the Federated States of Micronesia
“Over 200 acres of mangrove on the coastal reef fringe was reclaimed and was evidently well managed. Canals were left for access and drainage, local materials were used for pathways and wall infilling. Today, a thousand years later the only poor management aspect manifests itself in the collapse of some walls presumably due to compaction.”
“Today, the reality is that capacity to cope is much reduced for many as the island vulnerability has increased and continues to increase not the least due to exposure to the adverse impacts of climate change. The SOPAC director said revelations in the science journal publication undermine the urgent need to strengthen the science policy linkages.
“In particular, the negative press on this article works to jeopardise the efforts of Pacific Island governments in their preparations and negotiations leading to the UNFCCC Meeting in Cancun Mexico late this year. Howorth, however admits that the journal report is part and parcel of a larger jigsaw puzzle of the knowledge base, ‘which is still at best still in minimal.’
“The reality is we need to understand fully all the pieces in the jigsaw, and then we may develop an understanding of how they fit together to complete the picture. Last month, a BBC report quoting an article from the New Scientist said the islands of Tuvalu, Kiribati and the Federated States of Micronesia will remain 100 years time but not sure whether they will be inhabitable.
The study of 27 islands over the last 60 years, the report said, suggests that most have remained stable while some have actually grown. SOPAC has for nearly 40 years built a strong reputation for doing sound scientific and technical work in the Pacific….PNS (ENDS)
Below is the full text of the peer review by Aurthur Webb Arthur Webb: A brief on the peer reviewed, scientific publication The dynamic response of reef islands to sea-level rise: evidence from multi-decadal analysis of island change in the Central Pacific Webb & Kench, 2010. Global & Planetary Change (accepted).
Background and Methods This research paper describes the results of investigation into historical trends of atoll island shoreline change using historical aerial photography compared over time - the paper does not predict future response of shorelines and only documents past response. Depending on available records the studies look back in time from 20 to 60 years and covers atoll islands from Federated States of Micronesia, Kiribati and Tuvalu.
It is the first research in the world to address, from a holistic empirical perspective, how atoll shorelines have been responding to sea-level rise over the past half century. Records and estimations of the rate of sea-level rise are available in the literature but there is much variability.
The best estimates for the central Pacific which correspond to the period covered by the historical images suggest there has been approximately 120 mm of sea-level rise over this period. Whilst rates of sea-level rise have accelerated over the last century, the rates reviewed in this paper are in agreement with historical rates considered by IPCC 2007.
Historical aerial photographs exist for some Pacific Islands from the early 1940’s to the present and these offer an invaluable opportunity to look back in time to understand how islands have responded to historical sea-level rise up until present times.
The historical photos are compared using highly accurate satellite images which when processed and combined in computer mapping systems (GIS), allow measurement of change in shoreline position with accuracy and confidence. Where possible, field trips were also undertaken to confirm these results.
The results tell a remarkable story of atoll island shoreline stability and resilience over the last 20 to 60 years and this was unexpected given accompanying sea-level rise of around 120 mm.
To understand if the total land area of each island was getting larger or smaller, the entire island area was measured at different historical times. The analysis included all erosive, accreting (building) and stable beaches (not just individual beaches).
The results highlighted examples of both island accretion (islands increasing in area) and erosion (islands getting smaller in area), however when all of the data was combined the average rate of island area change showed that 86% of islands had remained relatively stable or increased in area and only 14% of islands had eroded or become smaller in total land area.
There was also some evidence that showed islands are tending to erode more on their ocean side shores and are accreting more on their lagoon side shores however this was very variable. It is not understood if this possible pattern of shifting away from the ocean and towards the lagoon may be a response to sea-level rise but it is possible.
It will be extremely important to continue monitoring this possible trend as such information would be a critical component of adaptation response and planning on these islands (at least in the immediate term).
The islands studied also included both inhabited and uninhabited islands to try and reveal any relationship between human activities and natural processes; urbanised islands tended to have large increases in area which was partly due to engineering however some of the largest increases in area also occurred in uninhabited islands with no engineering.
Whilst the shorelines of these atolls appear to have responded to historical rates of sea-level rise and the average change in island land area has so far been positive, it is not known how long this trend will continue or if this pattern is similar across the whole Pacific region.
There are a range of other climate change stresses which may disrupt shoreline processes; e.g. sea surface temperature increase, ocean acidification, accelerating rates of sea-level rise and possible changes in storm frequency or intensity.
Any of these or a combination may result in overwhelming the present resilience of these shorelines and if such a “tipping point” is reached, these atoll shorelines could become rapidly erosive. Now that these images have been processed they form the baseline (starting point) for on-going monitoring.
Every time new aerial photography or satellite imagery is acquired or available for any of these established islands it can be added to this system to provide updates on how shorelines are continuing to respond.
We will be able to detect if there are dramatic changes or other trends such as a gradual shifting of the island towards the lagoon (i.e. eroding on the ocean side coast and accretion (building) on the lagoon side.
This form of monitoring can also highlight urban impacts such as beach mining or inappropriate coastal engineering which tends to cause intense localised erosion or disturbance. It can also highlight unstable areas informing development planning.
Does this information change the vulnerability of the atolls to sea-level rise?
This study did not measure vertical growth of the island surface nor does it suggest there is any change in the height of the islands. Since land height has not changed the vulnerability of the greater part of the land area of each island to submergence due to sea-level rise is also unchanged and these low-lying atolls remain immediately and extremely vulnerable to inundation or sea water flooding.
Why is the data useful?
This information and data is crucially important for Governments and atoll communities, technical authorities, advisers and others who implement shoreline adaptation or development projects in the Pacific atolls. Accurate information informs appropriate adaptation responses and planning in the shoreline zone.
Previous assumptions that all atoll shorelines were erosive or alternatively that all erosion problems are caused by sea-level rise are inaccurate and cripple our ability at a technical level to effectively design and implement appropriate shoreline protection and adaptation responses. This study underlines the importance of protecting resilient shorelines from other human impacts; e.g. beach sand and gravel mining, poor engineering, reclamation, etc.
Since we still have many functional shoreline systems, priority should be given to their protection from disturbance so that they can continue to provide better protection from waves for a long as possible.
These shoreline monitoring efforts are ongoing; they are currently the only sustained efforts of their type in the world providing accurate information on shoreline response to a range of stresses in central Pacific atolls...PNS (ENDS)