Biodiversity Loss by Riverbank Erosion: A Study on the two Char Unions in Bangladesh

ISSN: 2332-2543

Journal of Biodiversity & Endangered Species

  • Research Article   
  • J Biodivers Endanger Species 2018, Vol 6(1): 209
  • DOI: 10.4172/2332-2543.1000209

Biodiversity Loss by Riverbank Erosion: A Study on the two Char Unions in Bangladesh

Muhammad Muzibur Rahman1* and Nazrul Islam M2
1Department of Geography and Environment, National University, Gazipur, Bangladesh
2Department of Geography and Environment, Jahangirnagar University, Savar, Dhaka, Bangladesh
*Corresponding Author: Muhammad Muzibur Rahman, Department of Geography and Environment, National University, Gazipur, Bangladesh, Tel: +880-1824-841299, Email: [email protected]

Received Date: Jan 22, 2018 / Accepted Date: Feb 07, 2018 / Published Date: Feb 13, 2018

Abstract

This study has explored the biodiversity loss of Lesraganj and Sutalari char unions through field survey, field observation technique and using BBS data. Bank erosion has destroyed the “habitat” of flora and fauna by disturbing the whole ecosystem chain of the study site. Many fruit varieties were available in mainland among which Jam, Amloki, Jalpai, Dalim, Chalta, Sharifa, and Latkan were not seen in the Charland. All types of homestead palm varieties have been lost while only banana is extensively practiced in the Charland. The mainland was rich in herbs and shrubs, but bank erosion has extinct them completely. The char dwellers are not capable to introduce any aesthetic varieties in the char homesteads and no aquatic vegetation could survive. The many mainland timbering yielding varieties are not found in the Charland except Eucalyptus and Babla while the mainland natural medicinal species cannot survive in the newly formed Charland. The mainland common mammalian fauna and birds are not found in the Charland due to the habitat damage. The mainland was rich in reptiles and amphibian species most of which have become very rare in the degraded char environment.

Keywords: Bank erosion; Biodiversity loss; Mainland; Charland; Habitat damage

Introduction

Natural hazards cause biodiversity loss and vice-versa. The various human activities and natural disruptions degrade ecosystem [1,2]. Bank erosion is a natural hazard, which destroys the existing biodiversity and/or ecosystem services of an area. Direct effects of biodiversity loss by bank erosion include an increased risk of sudden environmental changes- vulnerability to natural disasters (floods, droughts, and erosion), wildfires, disease, and access to clean water and raw materials, and food and energy security; decrease the regulation capability of regional or local climate [3,4]. In brief, the most adverse consequences of bank erosion are the “habitat loss” of flora and fauna by disturbing the whole ecosystem chain or safety net [5-7]. The bank erosion turns the healthy environment into a barren land or vacuum place with only a very few organisms or species [8].

This study has explored biodiversity loss of Lesraganj and Sutalari char unions of Harirampur Upazila on the Padma riverbed in Bangladesh (Figure 1). The study area (located between 23038/ and 23044/ north latitudes and between 89050/ and 90000/ east longitudes) is the isolated island. The island chars are very unstable because frequent erosion and regular sand carpeting changing the physical properties. The soils are seasonally flooded, have loamy to silty, and silty to silty textures and low organic matter contents [9-13]. The bank erosion has caused physical changes by eroding huge landmass, population displacement and damaging the natural environment and resources, therefore, the poor char community faces the challenges to meet their family needs including food, fuel and fodder. More importantly, the erosion has disturbed the whole ecosystem and spatially caused the habitat damage, which has exhausted the biological diversity. Before erosion, the study area was rich habitat where many species of flora and fauna co-exist but after erosion, the number of species, variety and variability of living organisms has been lost. This study has identified pre-existing biodiversity and biodiversity loss between the mainland and Charland considering the bank erosion as a root cause of the loss.

biodiversity-endangered-Lesraganj-Sutalari

Figure 1: Biodiversity loss of Lesraganj and Sutalari char unions of Harirampur Upazila on the Padma riverbed in Bangladesh.

Materials and Methods

This study has conducted questionnaire survey among the char dwellers on the biodiversity loss issue. The two char unions consist of 25 mouzas. Five questionnaires were filled in each mouza that method provided 125 questionnaires for better coverage of nature. The respondents were selected by stratified sampling technique to pick up the real-world information. Two sessions of focus group discussion were held in the two char unions. Each session consisted of 15 char dwellers including all types of professional char people (Farmers, fisherman, boatman, day laborer’s and teacher). Three expert officials of District Agriculture Extension Office (DAEO), District Animal Office (DAO) and Department of Environment (DoE) were employed to conduct a focus group discussion session significantly for achieving the real loss scenario. The Bangladesh Bureau of Statistics [14] provided the mainland fauna and flora list that were critically compared and examined in the char lands for identifying the lost varieties/species. The study has extensively performed field observation technique covering the whole year. The study team observed the Charland six times (two months interval) particularly in the dry season, spring and rainy (wet) season. Each time the survey team stayed ten or twelve days in hardship of the Charland. The seasonal observation technique has provided the information on the char physical environment and its associated flora and fauna varieties. The different char practitioners accompanied the survey team in performing the field observation technique.

Results and Discussion

Loss of fruit varieties

The common fruit varieties were available in the homesteads of the mainland. Among the mainland fruit varieties, Jam (Syzygium cumini), Amloki (Phyllanthus emblica), Jalpai (Elacocarpus floribundus), Dalim (Punica granatum), Chalta (Dillenia indica), Sharifa (Annona squanaosa) and Latkan (Bixa orellana) are completely absent in the char areas (Table 1).

English or Local Name Scientific name Pre-erosion Post-erosion Present Status of Species
Mainland Charland Lost Introduced
Papaya Carica papaya Planted Planted - -
Litchi Litchi chinensis Planted Planted - -
Mango Mangifera indica Planted Planted - -
Jackfruit Artocarpus heterophyllus Planted Planted - -
Guava Psidium guajava Planted Planted - -
Boroi Zizyphus mauritiana Planted Planted - -
Bel Aegle marmelos Planted Planted - -
Amra Spondias pinnata Planted Practiced - -
Kamranga Averrhoa carambola Planted Practiced - -
Jam Syzygium cumini Planted Not Planted Lost -
Amloki Phyllanthus emblica Planted Not Planted Lost -
Jalpai Elacocarpus floribundus Planted Not Planted Lost -
Dalim Punica granatum Planted Not Planted Lost -
Chalta Dillenia indica Planted Not Planted Lost -
Sharifa Annona squanaosa Planted Not Planted Lost -
Latkan Bixa orellana Planted Not Planted Lost -

Table 1: Loss of fruit varieties in study area.

Loss of homestead plants

After erosion, all sorts of palm plants have lost identity to the char community (Table 2). Though Bamboo (Bambusa bambos) is the most useful material to build households dwellings unit and other homestead activities, the char community has not raised any bamboo thickets in the homestead which was very common in the mainland.

Local or English Name Scientific Name Pre-erosion Post-erosion Present Status of Species
Mainland Charland Lost Introduced
Bamboo Bambusa bambos Presence Absence Lost -
Banana Musa paradisiaca Presence Presence - -
Date palm Phoenix sylvestris Presence Absence Lost -
Palmyra palm Borassus flabellifer Presence Absence Lost -
Coconut Cocos nucifera Presence Absence Lost -
Betelnut Areca catechu Presence Absence Lost -
Gab Diospyros peregrina Presence Absence Lost -
Dumur Ficus hispida Presence Absence Lost -

Table 2: Loss of homestead plants in study area.

Banana (Musa paradisiaca) was usually grown both in the mainland and in the Charland [15]. The char community stated that a special variety of banana thickets close to the vicinity of the dwellings protects the dwelling units from erosion during the rainy season.

Loss of homesteads vegetation

The soil properties and relief, rainfall, temperature and humidity influence the diversity of vegetation cover in any locality [16]. The mainland was rich in herbs and shrubs (Table 3). But bank erosion has caused the loss of herbs and shrubs in the Charland radically [17]. Only the Hogla (Typha angustata) and Dhoincha (Sesbania sesban) have survived in the Charland.

Local Name Scientific Name Pre-erosion Post-erosion Present Status of Species
Mainland Charland Lost Introduced
Kata Mehndi Duranta repens Presence Absence Lost -
Phani Mansa Opuntia dillenii Presence Absence Lost -
Arhar Cajanas cajan Presence Absence Lost -
Hogla Typha angustata Presence Presence - Introduced
Dhoincha Sesbania sesban Presence Presence - Introduced
Satamuli Asparagus racemosus Presence Absence Lost -
Gulancha Tinospora cordifolia Presence Absence Lost -
Kumarilata Smilax roxburghiana Presence Absence Lost -
Jangla shim Canavalia gladiata Presence Absence Lost -
Pui Azadirachta indica Presence Absence Lost -
Orchid Dendrobium aphyllum Presence Absence Lost -
Kochu Monochoria hastata Presence Absence Lost -

Table 3: Loss of homesteads vegetation in study area.

Loss of aesthetic species

The char dwellers could not able to introduce such varieties of flowers plants in their homesteads (Table 4). Firstly, the geoenvironmental conditions of the chars are not suitable for planting such types of varieties; secondly, the char community is at further risk of erosion which always makes them indifferent to planting the flower varieties for the beautification of their homesteads.

Local Name    Scientific Name Pre-erosion Post-erosion Present Status of   Species
Mainland Charland Lost Introduced
Hasnahena Cestrum nocturnum Practiced Not Practiced Lost -
Patabahar Codiaeum variegatum Practiced Not Practiced Lost -
Gandhoraj Gardenia jasminoides Practiced Not Practiced Lost -
Dolon Champa Hedychium coronarium Practiced Not Practiced Lost -
Kamini Murraya paniculata Practiced Not Practiced Lost -
Jaba Hibiscus rosa-sinensis Practiced Not Practiced Lost -
Madhumalati Chilonias hybridus Practiced Not Practiced Lost -
Togor Tabemaemontana divaricata Practiced Not Practiced Lost -
Shefali Erythrina stricta Practiced Not Practiced Lost -
Beli Jasminum sambac Practiced Not Practiced Lost -
Aparajaya Clitoria ternatea Practiced Not practiced Lost -
Sandhya malati Mirabilis jalapa Practiced Not Practiced Lost -

Table 4: Loss of homestead aesthetic species in study area.

Loss of aquatic vegetation

The water-loving aquatic vegetation was found along the narrow water places of the mainland. The ten aquatic varieties were richness (Table 5) among which nine variety could not survive in the Charland. Only the Noll khagra (Phragmites karka) were seen scattered in the low land areas which lush only in the rainy season (Table 5). The cause of absence of varieties is any back swamp has not developed in the char areas and even artificial ponds have not been dug in the char area hence the floating macrophytes and ferns have not been able to grow in the non-aquatic environment.

Local Name Scientific Name Pre-erosion Post-erosion Present Status of Species
Mainland Charland Lost Survived
Kachuri pana Eichhornia crassipes Presence Absence Lost -
Topa pana Pistia stratiotes Presence Absence Lost -
Khudi pana Lemna perpusilla Presence Absence Lost -
Paniphal Trapa bispissosa Presence Absence Lost -
Panchuli Nymphoides Presence Absence Lost -
Padma Nelumbo nucifera Presence Absence Lost -
Shapla Nymphaea nouchali Presence Absence Lost -
Kalmi Ipomoea aquatica Presence Absence Lost -
Helencha Enhydra fluctuans Presence Absence Lost -
Noll khagra Phragmites karka Presence Presence - Survived

Table 5: Loss of aquatic vegetation in study area.

Loss of medicinal vegetation

The various natural medicinal species could grow in the mainland and they dominated in different habitats and microhabitats. But the Padma River has eroded the plain land of Harirampur Upazila, therefore, the important biological resources of the mainland have been lost and a few new varieties have grown in the emerged char areas (Table 6). There were many vegetation species in the mainland vitally important to humans because many cures for human diseases have been found in these vegetation species [18].

Local Name Scientific Name Pre-erosion Post-erosion Present Status of Species  
    Mainland Charland Lost Survived
Bashak Adhatoda vasica Presence Absence Lost -
Thunkuni Centella asiatica Presence Absence Lost -
Datura Datura metel Presence Absence Lost -
Kesaraj Eclipta alba Presence Presence - Survived
Tulsi Ocimum sanctum Presence Absence Lost -
Dando kolosh Leucas lavandulifolia Presence Absence Lost -
Durba Cynodon dactylon Presence Presence - Survived
Gandho bhadali Cyperus difformis Presence Absence Lost -
Nisinda Vitex negundo Presence Absence Lost -
Kata-khoria Amaranthus spinosus Presence Presence - Survived
Shechi Dentella repens Presence Absence Lost -
Goicha Eragrotis spp. Presence Absence Lost -
Baita shak Chenopodium album Presence Absence Lost -
Noll ghash Hamerthria protensa Absence Presence - Survived
Son ghash Imperata cylindrica Absence Presence - Survived
Kysha Phragmites karka Absence Presence - Survived
Kash Saccharum spontaneum Absence Presence - Survived

Table 6: Loss of medicinal vegetation.

Loss of timber yielding plants

The good number of timber yielding varieties was planted in the mainland (Table 7). The mainland timber varieties were not planted and even a few could not survive naturally in the Charland. The char dwellers planted only the Eucalyptus (Eucalyptus globules) and the Babla (Acacia nilotica) in the Charland (Table 7).

Local Name Scientific Name Pre-erosion Post-erosion Present Status of Species
Mainland Charland Lost Introduced
Arjun Terminalia arjuna Practiced Not Practiced Lost -
Chatim Alstonia scholarsis Practiced Not Practiced Lost -
Pitraj Aphanamixis polystachya Practiced Not Practiced Lost -
Hijol Barringtonia acutangula Practiced Not Practiced Lost -
Simul Bombax ceiba Practiced Not Practiced Lost -
Neem Azadiracta indica Practiced Not Practiced Lost -
Tentul Tamarindus indica Practiced Not Practiced Lost -
Sajna Moringa oliefera Practiced Not Practiced Lost -
Jarul Lagerstroemia speciosa Practiced Not Practiced Lost -
Mandar Erythrina fusca Practiced Not Practiced Lost -
Kadam Anthocephalus chinensis Practiced Not Practiced Lost -
Palash Butea monosperma Practiced Not Practiced Lost -
Debdaru Polyalthia longifolia Practiced Not Practiced Lost -
Krishnachura Delonix regia Practiced Not Practiced Lost -
Akashmoni Acacia auriculiformis Practiced Not Practiced Lost -
Mahagoni Swietenia mahagoni Practiced Not Practiced Lost -
Sisso Dulbergia sissoo Practiced Not Practiced Lost -
Silkoroi Albizia procera Practiced Not Practiced Lost -
Randi Koroi Samanea saman Practiced Not Practiced Lost -
Eucalyptus Eucalyptus globulus Practiced Practiced - Introduced
Babla Acacia nilotica Practiced Practiced - Introduced

Table 7: Loss of timber yielding plants in study area.

The char dwellers expressed the Eucalyptus and the Babla can easily and swiftly grow in the sandy soil where other species cannot do. The Eucalyptus might be adaptable to the aquatic environment especially in the high flooding conditions and must be protective of the char erosion The Babla can survive in dry hot summer in char areas because of its arid or semi-arid characteristics. Another reason of planting the Babla is that the thorny character protects it from damaging or destroying by the grazing of livestock in the char areas.

Loss of mammals

The Bengal fox (Vulpex bengalensis), Common mongoose (Herpestes edwarsi), the common Otter (Lutra lutra), five striped Palm Squirrel (Funumbalus pennant), Common house rat (Rattus rattus), House Mouse (Mus musculus) Rhesus Monkey (Macaca mulata), Bat (Desmodus rotundus), jungle Cat (Felis chaus), small Indian Civet (Viverricula indica), large Bandicoot (Bandicota indica) and Jackal (Canis aureus) were available in the mainland before erosion (Table 8) because the congenial environment favored them living and breeding. Among the thirteen mammals of the mainland only the four mammals’ i. e., Cat (Felis chaus), small Indian Civet (Viverricula indica), large Bandicoot (Bandicota indica) and Jackal (Canis aureus) are now seen in the Charland. The river erosion degraded the local environment and caused the habitat damage which is the most influential drivers of mammals’ loss in the Charland.

English Name Scientific Name Pre-erosion Post-erosion Present Status of Species
Mainland Charland Lost Survived
Bengal Fox Vulpex bengalensis Presence Presence - Survived
Common mongoose Herpestes edwarsi Presence Presence - Survived
Palm Squirrel Funumbalus pennanti Presence Absence Lost -
Common Otter Lutra lutra Presence Absence Lost -
Common house rat Rattus rattus Presence Presence - Survived
House Mouse Mus musculus Presence Presence - Survived
Indian Parcupine Histrix indica Presence Absence Lost -
Rhesus Monkey Macaca mulata Presence Absence Lost -
Bat Desmodus rotundus Presence Absence Lost -
Jungle Cat Felis chaus Presence Absence Lost -
Small Indian Civet Viverricula indica Presence Absence Lost -
Large Bandicoot Bandicota indica Presence Absence Lost -
Jackal Canis aureus Presence Absence Lost -

Table 8: Loss of mammals’ types in study area.

Loss of birds

There are many common birds were found in the mainland (Table 9). Because all sorts of environmental advantages like safe habitat, food and breeding places were friendly present there. Among the bird varieties, only Brahminy Kite, common Kingfisher, spotted Dove, Pond Heron, and Pigeon have been seen in the char areas (Table 9). But these species are now vulnerable and will be newly endangered if the changing environment cannot recover the lost species.

English Name Scientific Name Pre-erosion Post-erosion Present Status of Species
Mainland Charland Lost Survived
House Crow Corvus splendens Presence Presence - -
House Sparrow Domesticus indicus Presence Presence - -
Bhat Shalik Acridotheres tristis Presence Presence - -
Black Drongo Dicrurus adsimilis Presence Presence - -
Reduented Bulbul Pycnontus bengalensis Presence Presence - -
Doel Copsychus saularis Presence Absence Lost -
Common weaver bird Ploceus phillippinus Presence Absence Lost -
Woodpecker Dinopium benghalense Presence Absence Lost -
Little Cormorant Phalacrocrax niger Presence Absence Lost -
Breasted water Hen Amauronis fiscus Presence Absence Lost -
Hawk Cuckoo Cuculus varius Presence Absence Lost -
Barn Owl Tyto alba Presence Absence Lost -
Brahminy Kite Haliaster indus Presence Presence - -
Common Kingfisher Alcedoathis bengalensis Presence Presence - -
Spotted Dove Streptopelia chinensis Presence Presence - -
Pond Heron Ardeola grajii Presence Presence - -
Pigeon Columba livia Presence Presence - -

Table 9: Loss of bird species in study area.

Loss of reptiles and amphibians

Amphibians and reptiles are particularly sensitive to changes in the environment [19]. The char land is subject to grazing, trampling, soil erosion and other biotic pressures [20]. Before erosion, the mainland was rich in reptiles and amphibian species. But after erosion, most of them have become very rare in the char environment (Table 10).

Local or English Name Scientific Name Pre-erosion Post-erosion Present Status of Species
Mainland Charland Lost Survived
Geckoes or Tik-tiki Hemidactylus spp. Presence Presence - -
Tokkay Gecko verticillatus Presence Presence - -
Yellow Monitor Varanus bengalensis Presence Absence Lost -
Grey land Monitor Testudo elongata Presence Absence Lost -
Ghargini Lycodon jara Presence Presence - -
Gokhra Naja naja Presence Presence - -
Dhora Shap Cerberus rhynchops Presence Absence Lost -
Paina Shap Enhydris enhydris Presence Absence Lost -
Rat Snake Dtyas mucosus Presence Absence Lost -
Bended Krait Bungarus fasciatus Presence Absence Lost -
Pond Tortoise Chitra indica Presence Absence Lost -
Common roof turtle Anthocephalus kadamba Presence Presence - -
Kuno Bang Bufo melanostictus Presence Presence - -
Bhawa Bang Rana tigrina Presence Absence Lost -
Kotkoti Bang Rana cyanophlyctis Presence Presence - -

Table 10: Loss of reptiles and amphibians.

Conclusion

The mainland was rich in different flora and fauna types, but bank erosion has acted as a driver to decrease the number or extinct of biodiversity because the mainland biomes could not survive in the degraded char environment. The biodiversity loss in the study area has been directly related to habitat destruction and/or damage of breeding and living places of flora and fauna species. Therefore, the biological resources of the mainland have not been able to adapt and creation of new generation making a colony in the degraded char environment. Bank erosion has caused radical changes of the zoo-geo-environmental habitat of the mainland which is the cause of the extinction of the biological diversity. This process could weaken the whole ecosystem, identified as mass extinction of the char ecosystem, and broken down the environmental stability. It is essential to reconstruct the degraded char environment by planting, harvesting and nursing the flora and fauna species so that the reconstructed ecosystem services may enrich the environment of the study area.

References

Citation: Rahman MM, Islam MN (2018) Biodiversity Loss by Riverbank Erosion: A Study on the two Char Unions in Bangladesh. J Biodivers Endanger Species 6: 209. Doi: 10.4172/2332-2543.1000209

Copyright: ©2018 Rahman MM, et al. This is an open-access article distributed under the terms of the creative commons attribution license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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