A DPSIR analysis of aeolian sand dune mobilization along the coast of Manawatu-Wanganui in New Zealand

Sampath, Dissanayake Mudiyanselage Ruwan; Freitas, Joana Gaspar de

Sampath, Dissanayake Mudiyanselage Ruwan,Freitas, Joana Gaspar de · 2020

Abstract

Coastal sand dunes are multifunctional landscapes with rich biodiversity and provide ecological goods and services. They play a dual role as a sediment sink or a source to maintain the long-term stability of a coastal system. These landscapes have been affected by human settlements, economic activities and recreational purposes. Sand dunes in the Manawatu-Wanganui region, in New Zealand, have been subjected to such forcings during Maori settlements and, in particular, since the establishment of Europeans since 1840. Consequently, dunes have evolved from a transgressive system to a parabolic one, while the rate of dune drifting is still observed to be one of the highest in the world. Because this was a problem for populations living in the area, there were several attempts to arrest dune drifting. Using the Driver-Pressure-State-Impact-Response (DPSIR) cyclic framework, we analyzed these interventions during two-time frames: 1) from the 19th to 20th century and 2) during the early 21st century. We checked for data in historical records and literature including the Parliamentary debates of New Zealand. Historical evolutionary trends were inferred by analyzing a series of maps since 1773. The present-day impacts were derived from a series of georeferenced google images from 1983 using the ESRI ArcGIS tools. The coastal management responses were obtained through scientific literature and reports of the Horizon Regional Council. According to the analysis, drivers of dune drift before the 21st century were 1) settlements resulting in burning shrubs, deforestation, grazing, agriculture, mining, and building, 2) introduction of non-native animals. The pressures were: 1) mobile dunes and 2) blowouts. The assessment of the state of the environment included: 1) soil fertility, 2) habitat quality, 3) river navigability and 4) air quality. The assessed impacts were 1) increase of wasteland and loss of fertility, 2) foredune erosion, 3) impact on transportation and 4) creation of swamps as river mouths were closed. The management responses included 1) introduction of 1903 and 1908 Sand Drift acts for reclamation of affected areas, 2) introduction of exotic vegetation (e.g. Marram grass) and 3) foredune building using sand trapping fences. The main drivers of the 21st century are 1) intensive urbanization, 2) introduction of exotic vegetation and 3) global fossil fuel burning. The invasive character of marram resulted in the loss of biodiversity. The coastline erosion due to sea-level rise during the 21st century will be moderated due to its progradational nature. The study revealed a significant spatial variability of the rate of dune drift. The responses include 1) a consolidated “One Plan” as mandated by 1991 Resource Management Act; 2) removal of exotic vegetation to support native biodiversity by enhancing natural processes of dunes (a paradigm shift in dune management); 3) enhancing awareness while encouraging the public participation in mitigating measures. In conclusion, historical data combined with DPSIR framework tools showed that management interventions should be implemented considering long-term and interdisciplinary analysis to better understand the systems’ evolution and the full consequences of human actions.

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A DPSIR analysis of aeolian sand dune mobilization along the coast of Manawatu-Wanganui in New Zealand

Author: Sampath, Dissanayake Mudiyanselage Ruwan,Freitas, Joana Gaspar de

Year: 2020

Source: https://repositorio.ulisboa.pt/bitstream/10451/46329/1/EGU2020-19785-print%2520%2528final%2529.pdf

EGU2020-19785
h ps://doi.o g/10.5194/egusphe e-egu2020-19785
EGU Gene al Assembly 2020
© Au ho (s) 2020. This wo k is dis ibu ed unde
he C ea i e Commons A ibu ion 4.0 License.
A DPSIR analysis o aeolian sand dune mobiliza ion along he coas
o Manawa u-Wanganui in New Zealand
Dissanayake Mudiyanselage Ruwan Sampa h and Joana Gaspa de F ei as
Uni e si y o Lisbon, Cen e o His o y, Lisboa, Po ugal ([email p o ec ed])
Coas al sand dunes a e mul i unc ional landscapes wi h ich biodi e si y and p o ide ecological
goods and se ices. They play a dual ole as a sedimen sink o a sou ce o main ain he long- e m
s abili y o a coas al sys em. These landscapes ha e been a ec ed by human se lemen s,
economic ac i i ies and ec ea ional pu poses. Sand dunes in he Manawa u-Wanganui egion, in
New Zealand, ha e been subjec ed o such o cings du ing Mao i se lemen s and, in pa icula ,
since he es ablishmen o Eu opeans since 1840. Consequen ly, dunes ha e e ol ed om a
ansg essi e sys em o a pa abolic one, while he a e o dune d i ing is s ill obse ed o be one
o he highes in he wo ld.
Because his was a p oblem o popula ions li ing in he a ea, he e we e se e al a emp s o
a es dune d i ing. Using he D i e -P essu e-S a e-Impac -Response (DPSIR) cyclic amewo k,
we analyzed hese in e en ions du ing wo- ime ames: 1) om he 19 h o 20 h cen u y and 2)
du ing he ea ly 21s cen u y. We checked o da a in his o ical eco ds and li e a u e including he
Pa liamen a y deba es o New Zealand. His o ical e olu iona y ends we e in e ed by analyzing a
se ies o maps since 1773. The p esen -day impac s we e de i ed om a se ies o geo e e enced
google images om 1983 using he ESRI A cGIS ools. The coas al managemen esponses we e
ob ained h ough scien i ic li e a u e and epo s o he Ho izon Regional Council.
Acco ding o he analysis, d i e s o dune d i be o e he 21s cen u y we e 1) se lemen s
esul ing in bu ning sh ubs, de o es a ion, g azing, ag icul u e, mining, and building, 2)
in oduc ion o non-na i e animals. The p essu es we e: 1) mobile dunes and 2) blowou s. The
assessmen o he s a e o he en i onmen included: 1) soil e ili y, 2) habi a quali y, 3) i e
na igabili y and 4) ai quali y. The assessed impac s we e 1) inc ease o was eland and loss o
e ili y, 2) o edune e osion, 3) impac on anspo a ion and 4) c ea ion o swamps as i e
mou hs we e closed. The managemen esponses included 1) in oduc ion o 1903 and 1908 Sand
D i ac s o eclama ion o a ec ed a eas, 2) in oduc ion o exo ic ege a ion (e.g. Ma am g ass)
and 3) o edune building using sand apping ences.
The main d i e s o he 21s cen u y a e 1) in ensi e u baniza ion, 2) in oduc ion o exo ic
ege a ion and 3) global ossil uel bu ning. The in asi e cha ac e o ma am esul ed in he loss
o biodi e si y. The coas line e osion due o sea-le el ise du ing he 21s cen u y will be
mode a ed due o i s p og ada ional na u e. The s udy e ealed a signi ican spa ial a iabili y o
he a e o dune d i . The esponses include 1) a consolida ed “One Plan” as manda ed by 1991
Resou ce Managemen Ac ; 2) emo al o exo ic ege a ion o suppo na i e biodi e si y by
enhancing na u al p ocesses o dunes (a pa adigm shi in dune managemen ); 3) enhancing
awa eness while encou aging he public pa icipa ion in mi iga ing measu es.
In conclusion, his o ical da a combined wi h DPSIR amewo k ools showed ha managemen
in e en ions should be implemen ed conside ing long- e m and in e disciplina y analysis o
be e unde s and he sys ems’ e olu ion and he ull consequences o human ac ions.
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