0860-B2

Valuing the storm protection function of mangroves: a case study from India

Ruchi Badola, Kalpana Ambastha and S.A. Hussain 1


Abstract

Cyclone damage avoided because of the mangrove forests along the east coast of India in Bhitarkanika, in the state of Orissa was estimated in three selected villages in the year 2001-2. Assessment of the socio-economic status of the villages, the actual damage to houses, livestock, fisheries, trees and other assets owned by the people as well as the rate, level and duration of flooding was carried out. Eleven variables were used to compare the damage in villages that were protected by cyclones and that were not. Attitude surveys were carried out in 10% of households in 35 villages located in and around the Bhitarkanika Conservation Area to know the perception and attitudes of local people towards mangrove forests. The study revealed that the variables used to compare the damage due to the cyclone had either the lowest values for adverse parameters such as for damage to houses, or highest values for positive parameters such as crop yield, for the village that was totally protected by mangroves. Flooding in house premises and crop fields were found to be high for the villages without mangrove cover. The dyke constructed to prevent saltwater intrusion was not effective during cyclones. The people appreciated the functions performed by the mangroves in protecting their lives and property from cyclones and were willing to cooperate with the forest department for forest restoration.


Introduction

The term mangrove applies to around 68 halophytic species of trees and shrubs found in tropical coastal areas (Chapman 1975). Mangrove ecosystems are widely recognized as providers of a wide variety of goods and services to people. They provide optimal breeding, feeding and nursery grounds for many ecologically and economically important fish and shellfish species (Macnae 1974), as well as feeding ground for water birds. They protect fresh water resources against salt-water intrusion and the land from eroding waves and winds (Semesi 1998, Wolanski 1985). They are valuable source of fuel wood, fodder, timber and other natural products (Rosolofo 1997). However, despite centuries of biological research on mangroves (Rollet 1981) and in spite of an understanding and recognition of mangrove benefits, destruction of these ecosystems continues so much so that mangrove forests rank among the most threatened of coastal habitats (Saenger et. al. 1983).

The loss of mangroves could be attributed to information failure such as a general lack of awareness among people about the values of conserving mangroves ecosystems, market failures due to excessive abstraction of open-access resources, and intervention failure such as general ineffectiveness or absence of appropriate integrated resource management policies and inter-sectoral policy inconsistencies (Shine and de Klemm 1999). While formulating sustainable mangrove use policies, valuation of their uses and the services provided by them can help resource managers deal with the effects of market failures, by measuring their cost to society, which are generally hidden from traditional economic accounting (Daily et. al. 1997). This helps society to make informed choices about the trade-offs (Loomis 2000).

The undisturbed and natural mangrove forests or ecosystems act as seaward barrier, check the coastal erosion and minimize the tidal thrust or storm hit arising from the sea (McNae 1968). The degree of protection varies with the width of mangroves. Mangrove root systems retard water flow. Resistance to water flow serves to dissipate the energy of floodwaters, of particular service during cyclone (e.g. Gilbert et. al. 1998).

A super cyclone a wind speed of around 260 km/h, and a storm surge of about 10 m hit the Orissa coast in the month of October 1999. This storm traveled more than 200 km inland and within a period of 36 hrs ravaged more than 20 million ha of land, affected around 15 million people and caused the deaths of about 20 000 people and over 400 000 cattle.

The present study aimed to determine the difference in the damage due to the cyclone among areas that were in the cover of mangroves and areas that were far away from mangroves. It also assessed the perception and awareness among the local people regarding the contribution of mangroves in protecting their lives and property from cyclones.

Study area

The study was conducted in the Bhitarkanika Conservation Area (Figure 1), the second largest mangrove forest of mainland India, located in the eastern state of Orissa, between 860 45' E to 870 50' E longitude and 200 40' to 200 48' N latitude (Patnaik et. al. 1995). This mangrove ecosystem and the associated coast, harbours the highest diversity of Indian mangrove flora and fauna. The floral diversity of Bhitarkanika includes more than 300 plant species both mangrove and non-mangroves belonging to 80 families (Banerjee 1984). Mammals of Bhitarkanika are represented by 31 species belonging to 25 genera and 14 families (Patnaik et. al. 1995). The Bhitarkanika mangrove ecosystem has now been identified as one of the sites of International importance under the Ramsar convention, 1971.

The forests of Bhitarkanika provide subsistence requirements of timber, fuel wood, fodder, tannin, honey, and thatch for the local people (Chadah and Kar 1999). In the year 1975 the area was declared a wildlife sanctuary to protect the endangered saltwater crocodile (Crocodylus porosus). The sanctuary encompasses an area of 672 km2, with the core area of 145 km2 having the status of a National Park. It has a coastline of 35 km on its eastern side, which is a marine Sanctuary. The entire area is approximately 3000 km2 and is known as Bhitarkanika Conservation Area (BCA) (Figure 1).

The climate of the region is tropical with the prevalence of frequent cyclones particularly during the late monsoon period.

Methods

We used the damage cost avoided approach to value the storm protection function of the Bhitarkanika mangrove ecosystem. In this case since we had the recent incident of super cyclone of 1999 to compare the damages, actual estimates of damage avoided due to mangroves were estimated. Preliminary information was collected randomly by asking people regarding the losses incurred by them due to the cyclone. On this basis we tried to demarcate villages protected by mangrove cover and those that were not protected by mangrove, and compared the damages in the two areas. But since, saline embankments have already been constructed in and around the area almost in the entire coastal belt to prevent the intrusion of seawater, it was imperative, that the effects of dyke and mangroves be separated. Hence, the following four situations were identified:

Three villages, namely Bankual, Bandhamal and Singidi (Figure 1) were identified to represent the first, third and fourth situations respectively, but the second situation was dropped because of the fact that the dyke covers the entire mangrove area. To keep the intensity of impact as uniform as possible, all the three selected villages were equidistant from the seashore. The two villages outside mangrove covers were located close by, but both were far off from the forest in order to eliminate the effect of mangroves (Table 1).

Door to door survey was conducted and a 100% sampling of the households was done to assess the socio-economic status of the villages, the actual damage to houses, livestock, fisheries, trees and other assets owned by the people and the rate, level and duration of flooding. On the basis of the type of damage to houses, a composite score, the variable DR (Damage Rating), was developed for each of the household surveyed in the three villages. The scores were in a range of 0-19 depending on the intensity of damage. The value of 19 was for total collapse i.e. sum of damage to all the structures (thatch, poles, roof and beams and walls) of the house. SPSS software was used for data processing and One-Way Anova tests were performed to compare the means of various variables for the three villages.

Information was gathered by focused public interviews about the direction of entry of water and probable reasons for flooding. Household survey was conducted in thirty-five villages located in and around the Bhitarkanika Conservation Area during which data on socio-economics; resource use and attitudes were gathered through a questionnaire survey, which targeted 10% of the households. A set of semi structured along with a few open type questions were put up to know the perception and attitude of local people.

Results

Village characteristics

The general characteristics of the three study villages have been given in Table 1. As per the 1991 census the mean household size was 4.5 to 8.2. It was low for Bankual (4.2) in comparison to Singidi (8.2). The overall human density in the study villages ranges between 260-340 persons/km2. The literacy level was highest for Singidi and lowest for Bankual. In Singidi and Bankual majority of the people (70%) were engaged in agriculture, where as in Bandhamal around 61% were labourers. Most of the houses (94%)were made of mud and thatch.

Damage due to the cyclone

Damage to houses

Not many cases of damage to basic roof frames were reported. Only 17.5 % of the houses had been constructed within last three years (post cyclone period). However, in most of the houses (49.5%) roof thatch was blown away, accompanied by either cracking of walls, or their partial collapse on some sides. The maximum value of the scores i.e. maximum damage to the houses was 9.4 +0.71 for Singidi village- the village located in non-mangrove area, outside the dyke. The lowest 5.3 +0.58 was for Bankual i.e. the village in mangrove covers (Table 2). A significant difference was found in the means of the scores for the damage caused to houses for the three villages (F=14.633, df=2, p=0.000). The difference between Bankual and Singidi, and Bankual and Bandhamal was -4.0633 and -5.0954 respectively, which were significant at p=0.05 levels.

Reconstruction costs for houses damaged during the cyclone

The highest cost for reconstruction work per household was found to be Rs. 997.0 +182.18 (or US$ 21) for Singidi while the lowest Rs. 682.9 +144.05 (or US$ 15) for Bankual (Table 2).

Flooding in the villages

Flooding in house premises was highest in Bandhamal, the village protected by the dyke but without mangrove cover (0.6 m +0.054m), while lowest was for Bankual, village in mangrove cover (0.3 m +0.045 m). The highest level of flooding in the fields was for Singidi, village outside mangrove area and not protected by dyke, followed by Bandhamal and Bankual. The difference between flooding levels in fields was found to be significant for all the villages at 95% confidence level (F=35.102, df=2, p=0.000). The same was true for the level flooding in house premises. Floodwaters remained in fields for a maximum number of days in Bandhamal followed by Singidi and Bankual (Table 2).

Damage to crops

Following the cyclone the standing crop of paddy was severely affected and a significant difference between crop productions for the three study villages was seen at 0.05 levels, (F=7.239,df=1, p=0.008). The mean yield for year 1999 the three study villages was 568 kg/ha and that for 2001 it was 1012.7 kg/ha. The year 2001 was itself not considered a good year for the paddy crop, 71.6% of the people (n=67), who undertook cultivation complained of a poor harvest. The agricultural production in 1999 was highest in Bankual (1479.5 kg/ha) (Table 2).

Loss to fisheries, livestock and other assets

The highest damage to fish seedlings (fingerlings) was in Singidi where Rs 310.8 +144.97 worth of seedlings released were washed away. It was the lowest in Bankual (Rs.69.7 +32.20) (Table 2). Loss to private property was highest in Bandhamal. The maximum number of livestock casualties occurred in Bandhamal, followed by Bankual and Singidi. The percentage of trees dying due to cyclone was highest in Singidi. Only 3.3% trees were damaged in Bankual, which had the highest number of trees.

Total loss in money terms

The total loss in terms of rupees was obtained for each of the households in all the three villages by combining the money values of the following quantifiable variables:

Market value of loss of agriculture income with a target production of year 2001 i.e. the difference in total paddy production (2001-1999) taking the area cultivated in 1999 as a common factor

The loss incurred per household was found to be greatest in Bandhamal (Rs 6918.6 +114.20, US$147.2) Table 2.

Perception of people regarding the contribution of mangroves in their lives

When asked to rank the ecological performed by mangroves, first preference was given by the people to cyclone mitigation, with 89% respondent stating it as the first preference. The land erosion prevention function ranked second (Table 3).

Attitudes of people towards conservation

About 90% people in the area were aware that the Bhitarkanika forests have protected status. A high percentage (84%) of people felt responsible for the conservation of flora and fauna while 93% were in favour of an Integrated Conservation and Development Programme. c43% of people were willing to cooperate with forest department in this regard. Only 18% people felt a violation of their rights with the park's declaration, the main reason being the denied easy access to firewood (Table 4).

Discussions

The vulnerability of many coastal communities is heightened by the removal of coastal wetlands for crops and habitation. These wetlands are natural buffers against storm surges (Maltby 1986). Mangroves protect tropical shores from erosion by tides and currents, and Macintosh (1983) recommended that a mangrove strip at least 100 m wide should be left as a buffer zone on the more exposed shores.

Our findings indicate that mangroves help in reducing the influx of water as evident from lower levels of flooding in Bankual. Further they do not impede the slow recede of water from the houses and the fields. Flooding in Bankual was from the forest side when the creeks overflowed the banks during the high tide. The yield of paddy was found to be highest for Bankual and it may be inferred that it was easier to salvage the crop in the area.

No reports of breaches, in the dyke located around the forest area indicate the protection provided by mangroves to the dykes, although this is not conclusive as further data authentication is required. However, in areas far from the forest several breaches in the dyke were reported and this is reflected in higher levels of flooding and greater mean number of days of flooding in Bandhamal. Singidi with no mangrove cover and no dyke suffered the highest level of flooding in the fields and a medium one in the house premises. This is because the fields are located directly on the banks of the Kharsuan river but a 1m high village road offers some protection to houses. This shows that the forests were effective in preventing damage due to floods as compared to the dyke. In fact, the sluice gates were not opened many days after the flooding, which resulted in greater loss in the villages surrounded by the dyke.

The study of socio-demographic characteristics, economic situation, and other aspects of life in these mangrove villages reveal a high degree of resource use and dependence of the people on mangrove resources for their livelihoods. Bhitarkanika being a Ramsar site implies wise use of its resources. This is possible through careful planning, management, regulation or even prohibition of certain activities. This can effectively be made possible only through a proper consultation and agreement with the local communities. The appreciation of the functions performed by the mangroves by the local people is a positive sign for conservation of the area.

Costanza et. al. (1989) have concluded that ecological functions such as storm protection may be very important components in the total economic value of a wetland and may constitute almost 80% of the estimated value. During the present study a significant difference was found to exist among the variables examined to assess damage due to the cyclone, for the mangrove and non-mangrove areas. Because artificial sea defenses and river levees are expensive to build and repair, no-cost natural alternatives look very appealing. There is a growing awareness that trees adapted to water logged conditions are effective in controlling bank erosion and that conserving or even replanting wetland vegetation may be the most cost- effective solution to erosion problems in both freshwater and marine environments.

Acknowledgements

We thank the Indian Environment Management Capacity Building (EMCaB) Project, Indira Gandhi Institute of Development Research (IGIDR), Mumbai, for granting funding support for this study.

References

Banerjee, L.K. (1984). Vegetation of Bhitarkanika Sanctuary in Cuttack district, Orissa, India. Indian J. of Economic and Taxonomic Botany. Vol 5 (5); 1065-1079

Chadah, S. and Kar, C.S. (1999). Bhitarkanika, Myth and Reality. Natraj Publisher, Dehra Dun.

Chapman, V.J. (1975). Mangrove Biogeography. In: Walsh, G.E., Snedaker, S.C. and H.Teas (eds.). Proceedings of the International Symposium on Biology and Management of Mangroves, Honolulu, 8-11 October 1974, pp. 3-22.

Costanza, R., C. Faber, and J. Maxwell, (1989). The valuation and management of wetland ecosystems. Ecological Economics. Vol. 1; 335-361.

Daily, G.C., S. Alexander, P.R. Ehrlich, L.Goulder, J. Lubchenco, P.A. Matson, H.A. Mooney, S. Postel, S.H. Schneider, D. Tilman, G.M. Woodwell (1997). Ecosystem Services: Benefits supplied to human societies by natural ecosystems. Nature's Services: Societal Dependence on Natural Ecosystems. Island press, Washington, D.C.

Loomis, J.B. (2000). Can environmental economic valuation techniques aid ecological economics and wildlife conservation? Wildlife Society Bulletin. Vol. 28, No. 1; 52-60

Macnae, W. (1974). Mangrove forest and fisheries. FAO/UNDP Indian Ocean Fishery Programme. Indian Ocean Fishery Commission. Publication IOFCDev/74/ 34-35

MacNae, W. (1968). A general account of the Flora and fauna of Mangrove swamp and prospective in the Indo- West Pacific region. Adv. Mar. Biol. Vol. 6; 73-270 pp.

Maltby, E. (1986). Waterlogged Wealth. International Institute for Environment and Development, London and Washington, D.C.71-72 pp.

Pandav, B. 1996. Birds of Bhitarkanika mangroves, eastern India. Forktail 12: 7-20.

Patnaik, M.R., K.L. Purohit and A.K. Patra 1995. Mangrove swamps of Bhitarkanika, Orissa, India - A great eco habitat for wildlife. Cheetal. Vol. 34 (1)1-9.

Rollet, B. (1981). Bibliography on Mangrove Research, 1600-1975. UNESCO, Paris, France.

Rosolofo, M.V. (1997). Use of mangroves by traditional fishermen in Madagascar. Mangrove Salt Marshes J., 243-253

Saenger, P., Hegerl, E.J. and Davie, J.D.S. (1983). Global status of mangrove ecosystems. The Environmentalist: Supplement. Vol. 3; 49 pp

Semesi, A.K. 1998. Mangrove management and utilization in Eastern Africa. Ambio, Vol. 27 (8); 620-626

Shine, C. and C. de Klemm (1999). Wetlands, water and the law- using law to advance wetland conservation and wise use. IUCN Environmental policy and law paper, No. 38. IUCN - The World Conservation Union

Wolanski, E. (1985). Numerical modeling of flows in the tidal creek- mangrove swamp system. Proceedings 21st, Congress International Association for Hydraulic Research, Melbourne, Victoria. Vol. 3; 80-85

Table 1. General characteristics of the three study villages situated along the east coast of India.

Location details (km)

Singidi

Bankual

Bandhamal

Distance from mangrove forest

9.2

0

8.2

Distance from sea coast

12.65

12.13

12.18

Distance from dyke

No dyke

2.37

0.45

Demographic characteristics

Total area (ha)

122.63

55.75

147.27

Number of households

58

42

56

Mean household size

8.2

4.5

6.8

Total population

353

189

383

Literacy (%)

56.7

31.2

38.6

Human Density (persons/km2)

314

340

260

Economic characteristics

% of people involved in agriculture

70.6

70.6

14.4

% people involved in fishing, animal husbandry and allied activities

0

14.7

0

% people involved in labour

22.4

2.95

61.38

% of people involved in other activities

7.03

11.8

24.4

Table 2. Basic description of the variables (mean value) examined for comparing the damage due to the cyclone.

Variable

Description

Singidi

Bankual

Bandhamal

DR

Damage on a scale of 0-19 as indicator of extent of damage to houses

9.40

5.34

10.44

FP

Flooding in premises (m)

0.34

0.29

0.58

FF

Flooding in fields (m)

1.99

1.09

1.39

WLF

Water logging in fields (days)

9.46

5.63

12.87

CR

Cost of repair and reconstruction (Indian Rs)

996.97

682.86

973.21

PTD

% of tree damaged

21.0

3.3

15.5

Y99

Yield in kg/ha for the year 1999

1531

1479.5

335.9

LFS

Loss to fish seedlings (fingerlings) in money terms released prior to cyclone (Indian Rs)

310.81

69.74

260.94

DPP

Damage to other personal property (Indian Rs)

108.11

0.00

2375.00

DL

Damage to livestock in money terms (Indian Rs)

54.05

127.63

1044.37

TML

Total money worth of quantifiable variables (Indian Rs)

1983.36
(US$ 42.2)

1454.13
(US$ 30.9)

6918.62
(US$ 147.2)

Table 3. Ranking of various functions performed by the mangrove forests by the local people (n =268).

Ecological functions/values

Rank 1(%)

Rank 2(%)

Rank 3(%)

Cyclone mitigation

88.6

11

0.4

Land erosion prevention

50

50

0

Aesthetic

38

61.2

0.8

Historical

8.8

88.9

2.3

Nutrient retention

8

92

0

Fish production

1.9

96.2

1.9

Others

18.9

70.3

10.8

Table 4. Attitude of local people towards Bhitarkanika Wildlife Sanctuary and conservation initiatives.

Questions

Yes (%)

No (%)

Don't know/ Indifferent (%)

Are you aware that Bhitarkanika is declared National Park and Sanctuary?

89.6

10.4

0

Do you feel any sense of responsibility for the protection of diverse flora and fauna?

84.3

13.4

2.2

Do you think your rights have been violated after declaration of park?

18.3

72.8

9

Are you in favour of ecodevelopment project?

92.9

2.2

4.9

Would you like to co-operate with forest department in regard to ecodevelopment project?

43.3

23.1

36.6



1 Wildlife Institute of India, PO Box#18, Dehra Dun. 248 001, India. ruchi@wii.gov.in