Invasive Plant Species in Mangrove Wetlands: Patterns of Spread and Ecological Threats

Indian Journal of Advanced Botany (IJAB) ISSN: 2582-9475 (Online), Volume-5 Issue-2, October 2025 43 Published By: Lattice Science Publication (LSP) © Copyright: All rights reserved. Retrieval Number: 100.1/ijb.B106605021025 DOI: 10.54105/ijab.B1066.05021025 Journal Website: www.ijb.latticescipub.com Abstract: Biological invasions pose a serious threat to natural ecosystems. Mangroves are vulnerable to invasion by salt-tolerant aquatic and terrestrial plants, such as epiphytes, despite their extremely saline and intertidal habitat. The present study examines the invasion rates and assesses the ecological impacts of invasive plant species on the mangrove flora of Kannur District, Kerala. Extensive field visits were conducted in the selected study stations to analyse plant species using the line transect method. A total of 21 plant species, including 7 true mangroves and eight mangrove associates, were recorded from the study areas. Out of the identified plant species, 11 are invasive, belonging to 5 families and 11 genera. The highest invasion rate was observed in Ipomoea cairica (1.203) at site-2, followed by Volkameria inermis (4.404×10-1). The competition between invasive plants and native species for light, nutrients, and space impacts the growth, development, and diversity of mangroves. Well-framed policies and effective management strategies are vital to curb invasive plant spread and safeguard the long-term conservation of mangrove ecosystems. Keywords: Invasive Plants, Invasion, Mangroves, Wetland Nomenclature: ES: Exotic Species IS: Invasive Species TMs: True Mangrove Species MAs: Mangrove Associate Species RI: Rate of Invasion. IBIS: Indian Biodiversity Information System POWO: Plants of the World Online I. INTRODUCTION Mangrove ecosystems, which thrive primarily along tropical and subtropical coastlines, are currently in a state of severe degradation despite providing essential ecological services. Mangrove habitats are susceptible to plant invasion. Nonnative species introduced by humans to a new location beyond their natural distribution area, which seriously damage the environment, society, or economy, are known as Manuscript received on 01 October 2025 | Revised Manuscript received on 08 October 2025 | Manuscript Accepted on 15 October 2025 | Manuscript published on 30 October 2025. *Correspondence Author(s) Dr. Chandramohanan K T, Professor, Krishna Menon Memorial Government Womens College, Kannur, Kannur University, Kannur (Kerala), India. Email ID: [email protected], ORCID ID: 0009-0004-5155-3294 Swedha Madhavan M*, Scholar, Department of Botany, Government Brennen College, Thalassery, Kannur University, Kannur (Kerala), India. Email ID: [email protected], ORCID ID: 0009-0005-0128-0651 Dr. P Sreeja, Associate Professor, Sir Syed College, Thaliparamba, Kannur University, Kannur (Kerala), India. Email ID: [email protected], ORCID ID: 0000-0002-8163-9994 Sharfa Usman, Department of Botany, Sir Syed College, Thaliparamba, Kannur University, Kannur (Kerala), India. Email ID: [email protected] © The Authors. Published by Lattice Science Publication (LSP). This is an open-access article under the CC-BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) invasive alien plants [1]. Key characteristics of invaders include a high rate of development, high fecundity, efficient dispersal mechanisms, high seed production, and the ability to withstand a greater variety of environmental conditions [2] [3]. Invasive species spread easily through wind, water, and animals. Their fast growth allows them to outcompete slower-growing native plants, and they expand uncontrollably in new locations, especially where natural enemies or other controls are absent [3]. Invasive plants can flourish and compete in new habitats due to their superior resource acquisition traits, such as height, leaf thickness, water content, and photosynthetic rates, as well as their competitive abilities, which are influenced by traits like height, diameter, and biomass allocation [4] [5]. The invasion of alien species has a profound impact on ecosystem function and community structure, making it a serious global environmental concern. The ability of mangroves to act as carbon sinks is hampered by alien species invasion, which results in significant declines in the mangrove biomass and carbon stock of the soil and vegetation [6]. Around 17% of the global land is highly susceptible to plant invasion, potentially altering nutrient cycles and impacting greenhouse gas emissions in terrestrial and wetland ecosystems [7]. Invasive plants seriously threaten global biodiversity, yet little is known about their effects and traits. Mangroves are vulnerable to invasion by salt-tolerant aquatic and terrestrial plants, such as epiphytes, despite their extremely saline and intertidal habitat. The functional characteristics, invasion patterns, pathways, and ecological effects of these invasive species are not well understood [8]. Research on wetland invasive plants has identified various interacting mechanisms—resource availability, enemy release, phenotypic plasticity, and reproductive strategies—that influence their ecological and economic impacts. Recognising how these differ from upland invasions is crucial for effective management and guiding future research [9]. The present study is a preliminary investigation that focuses on identifying and documenting invasive plant species in the mangrove wetlands of selected stations in Kannur district, Kerala. It also compares the rate of invasion and its ecological impacts on mangrove plant species. II. MATERIAL S AND METHODS A. Study Area The selected study stations in Kannur district are Andalloor (S1)- 11°47'58.1"N 75°28'55.3"E Nadal (S2)- 11°49'07.1"N 75°25'57.0"E and Invasive Plant Species in Mangrove Wetlands: Patterns of Spread and Ecological Threats Chandramohanan K T, Swedha Madhavan M, P Sreeja, Sharfa Usman Invasive Plant Species in Mangrove Wetlands: Patterns of Spread and Ecological Threats 44 Published By: Lattice Science Publication (LSP) © Copyright: All rights reserved. Retrieval Number: 100.1/ijb.B106605021025 DOI: 10.54105/ijab.B1066.05021025 Journal Website: www.ijb.latticescipub.com Valapattanam (S3)- 11°56'01.6"N 75°21'10.3"E Satellite Google map images of the study stations are presented in Figures 1a, b., and c. B. Sampling Techniques and Species Identification Extensive field visits were conducted in the selected study stations to analyse plant species using the line transect method. A total of thirty sampling lines (10 per site, each 10 meters) were surveyed. Invasive plant species, along with true mangroves and their associates, were recorded. Identification of true mangrove species, associates, and invasive species was done based on online databases, such as Plants of the World Online (POWO), the Indian Biodiversity Information System (IBIS), and e-Flora Kerala [10], [11] & [12]. i. Vegetation Analysis and Rate of Invasion The Intensity of invasion, ecological association, and their impacts were studied by direct observation. ‘The rate of invasion is the change in the per cent cover of plants at which invasion occurs inside the forest from the forest border’ [13]. The rate of invasion (RI) is calculated using the following equation: RI = (∑(|𝐷𝑏−𝐷𝑚|)/𝑑)/ 𝑛 Db = Density of invasive species at the border of the forest. Dm = Density of invasive species at the middle of the forest. d = Distance between initial and end plot in meters. n = Number of sample lines covered III. RESULT AND DISCUSSION A total of 21 plant species, including 7 true mangroves and eight mangrove associates, were recorded from the study areas. Out of the identified plant species, 11 are invasive, belonging to 5 families and 11 genera. Out of these, 3 are exotic or alien invasive species, which include Acacia mangium, Gliricidia sepium, and Pennisetum polystachion. A list of all identified plant species, life form, family, and their status is given in Table 1. Among the identified invasive species, the family Fabaceae is represented by four species (37%). They are Acacia mangium, Derris trifoliata, Gliricidia sepium, and Mimosa pudica. Asteraceae by three species (27%), and they are Chromolaena odorata, Mikania scandens, and Sphagneticola trilobata. Then one each from Lamiaceae (9%) - Volkameria inermis, Convolvulaceae (9%) - Ipomoea cairica, Malvaceae (9%) - Urena lobata, and Poaceae (9%) - Pennisetum polystachion. Out of the recorded 11 invasive plant species, shrubs (27%)—Chromolaena odorata, Urena lobata, Volkameria inermis —constitute the primary category, followed by climbers (27%)—Derris trifoliata, Ipomoea cairica, Mikania scandens. Herbs (27%) - Mimosa pudica, Pennisetum polystachion, Sphagneticola trilobata, and trees (19%) - Acacia mangium, Gliricidia sepium. Seven true mangroves belonging to 4 families (Acanthaceae, Rhizophoraceae, Lythraceae, and Euphorbiaceae) were identified from the study stations. True mangroves identified from the study sites are Avicennia officinalis L. and Bruguiera cylindrica (L.). Blume, Acanthus ilicifolius L., Rhizophora mucronata Lam., Excoecaria agallocha L., and Kandelia candel (L.) Druce. Gliricidia sepium, Ipomoea violacea, Premna serratifolia, Sphagneticola trilobata, Volkameria inermis, and Wattakaka volubilis are the recorded mangrove associates from the study area. A total of 10 invasive plant species were identified at Site-1, including D. trifoliata, C. odorata, V. inermis, G. sepium, U. lobata, A. mangium, M. pudica, I. cairica, M. scandens, and S. trilobata. The highest invasion rate was observed in V. inermis (4.404×10-1), followed by M. pudica (3.748×10-1) and the others in descending order. Site-2 recorded five invasive species, with I. cairica (1.203) exhibiting the highest invasion rate. Site-3 also had five species, where P. polystachion (2.996×10-1) showed the highest invasion rate. Invasion rates of plants from each study site are presented in Table 2. [Fig.1: a, b, and c: Satellite Google Map Images of the Study Stations S1, S2, and S3] Derris trifoliata was found to be the most abundant invasive species in S1. Whereas in S2 and S3, Ipomoea cairica was found to be the most abundant invasive species. Sphagneticola trilobata in S1 and Acacia mangium in S2 and S3 are the least abundant species identified. Climbers and shrubs (3 out of 10) were the most common invasive species in S1, followed by herbs (2 out of 10) and trees (2 out of 10). Trees and climbers were highest in S2 (2 out of 5), followed by shrubs (1 out of 5). In S3 climbers (2 out of 5) were the most common invasive species. While herb, shrub, and tree occurred equally (1 out of 5). Invasive plants recorded from the study sites are presented in Figures 4. a-j. a b c Indian Journal of Advanced Botany (IJAB) ISSN: 2582-9475 (Online), Volume-5 Issue-2, October 2025 45 Published By: Lattice Science Publication (LSP) © Copyright: All rights reserved. Retrieval Number: 100.1/ijb.B106605021025 DOI: 10.54105/ijab.B1066.05021025 Journal Website: www.ijb.latticescipub.com Table 1: List of All Identified Plant Species, Life Form, Family, and Status from the Study Stations Sl No Plant Species Life Form Family Status 1 Acacia mangium Willd. Tree Fabaceae E, I 2 Acanthus ilicifolius L. Shrub Acanthaceae T 3 Avicennia officinalis L. Tree Acanthaceae T 4 Bruguiera cylindrica (L.) Blume Tree Rhizophoraceae T 5 Chromolaena odorata (L.) R.M.King & H. Rob. Shrub Asteraceae I 6 Derris trifoliata Lour. Climber Fabaceae I 7 Excoecaria agallocha L. Tree Euphorbaceae T 8 Gliricidia sepium (Jacq.) Kunth Tree Fabaceae A, E, I 9 Ipomoea cairica (L.) Sweet Climber Convolvulaceae I 10 Ipomoea violacea L. Climber Convolvulaceae A 11 Kandelia candel (L.) Druce Tree Rhizophoraceae T 12 Mikania scandens (L.) Wild. Climber Asteraceae I 13 Mimosa pudica L. Herb Fabaceae A, I 14 Pennisetum polystachion (L.) Schu Herb Poaceae E, I 15 Premna serratifolia L. Tree Lamiaceae A 16 Rhizophora mucronata Lam Tree Rhizophoraceae T 17 Sonneratia alba Sm. Tree Lythraceae T 18 Sphagneticola trilobata (L.) Pruski Herb Asteraceae A, I 19 Urena lobata L. Shrub Malvaceae I 20 Volkameria inermis L. Shrub Lamiaceae A, I 21 Wattakaka volubilis (L. f.) Stapf Climber Apocynaceae A The Line graph showing the rate of invasion of recorded invasives in the study stations is presented in Figure 2. Site-1 (Andalloor) is at a higher risk of invasion than Site-2 (Nadal) and Site-3 (Valapattanam). Most of the invasive species compete with native mangrove species for light and nutrients. Among the identified invasive species, climbers, herbs, and shrubs show a higher rate of invasion than trees. Due to the climbing nature of Derris trifoliata, it completely encircles and interferes with the host mangrove plant. It shows a high risk of physical damage to the native species, mainly to Rhizophora mucronata. Volkameria inermis also possesses a high risk of invasion in this area. These invasive species also compete with native plant species for space. The aggressive colonisation of Mikania scandens, with its ability to climb up to the canopy from forest fringes and spread over it, harms Avicennia officinalis. Ipomoea cairica, one of the major invasive species, forms a dense crown around the canopy of R. mucronata and other mangrove species in the S2 mangrove station. Invasion of Sphagneticola trilobata and Pennisetum polystachion, showing their extensive spread over the mangrove area, and the mangrove canopy is extensively overgrown and dominated by invasive climbing species, is presented in Figures 3a and b. In addition to these invasive plant species, several anthropogenic activities, including the disposal of non-biodegradable waste, road construction, sand mining, and land exploitation at the study stations, also pose threats to mangroves. IV. CONCLUSION The spread, growth, and threats from invasive species significantly reduce mangrove biomass productivity and disturb the ecological equilibrium. Invasive plants compete with native flora for light, nutrients, and space, causing physical stress and disrupting the natural regeneration of indigenous species. The invaders adversely affect the growth, development, and diversity of mangroves. All these factors significantly challenge biodiversity and ecosystem conservation. Therefore, detailed investigations on the ecological impacts of invasives, along with continuous monitoring, are essential. Furthermore, well-framed policies and effective management strategies are vital to curb invasive plant spread and safeguard the long-term conservation of mangrove ecosystems. Table II: Rate of Invasion of Plant Species in S1, S2, and S3 Sl No Invasive Species Rate of Invasion S1 S2 S3 1 Acacia mangium 1.968×10-1 7.074×10-2 7.885×10-3 2 Chromolaena odorata 2.439×10-1 1.698×10-1 0 3 Derris trifoliata 2.623×10-1 4.244×10-1 1.892×10-1 4 Gliricidia sepium 3.748×10-2 1.415×10-1 0 5 Ipomoea cairica 1.312×10-1 1.203 2.365×10-1 6 Mikania scandens 1.124×10-1 0 0 7 Mimosa pudica 3.748×10-1 0 0 8 Pennisetum polystachion 0 0 2.996×10-1 9 Sphagneticola trilobata 2.811×10-2 0 0 10 Urena lobata 8.432×10-2 0 0 11 Volkameria inermis 4.404×10-1 0 1.577×10-1 0.00 0.25 0.50 0.75 1.00 1.25 A. mangium C. odorata D. trifoliata G. sepium I. cairica M. pudica M. scandens P. polystachion S. trilobata U. lobata V. inermis Invasive Species Rate of Invasion Site S1 S2 S3 Rate of invasion of plant species at S1, S2 and S3 [Fig.2: Line Graph Showing the Rate of Invasion of Recorded Invasives in the Study Stations] Invasive Plant Species in Mangrove Wetlands: Patterns of Spread and Ecological Threats 46 Published By: Lattice Science Publication (LSP) © Copyright: All rights reserved. Retrieval Number: 100.1/ijb.B106605021025 DOI: 10.54105/ijab.B1066.05021025 Journal Website: www.ijb.latticescipub.com [Fig.3: a. Invasion of Sphagneticola Trilobata and Pennisetum Polystachion, Showing their Extensive Spread Over the Mangrove Area. b. The Mangrove Canopy is Extensively Overgrown and Dominated by the Invasive Climbing Species Mikania Scandens] [Fig.4: Invasive Plants Recorded from the Study Sites. a. D. trifoliata, b. V. inermis, c. A. mangium, d. M. scandens, e. C. odorata, f. S. trilobata, g. G. sepium, h. I. cairica, I. U. lobata, j. P. polystachion] DECLARATION STATEMENT After aggregating input from all authors, I must verify the accuracy of the following information as the article's author. ▪ Conflicts of Interest/ Competing Interests: Based on my understanding, this article has no conflicts of interest. ▪ Funding Support: This article has not been funded by any organizations or agencies. This independence ensures that the research is conducted with objectivity and without any external influence. ▪ Ethical Approval and Consent to Participate: The content of this article does not necessitate ethical approval or consent to participate with supporting documentation. ▪ Data Access Statement and Material Availability: The adequate resources of this article are publicly accessible. ▪ Author’s Contributions: The authorship of this article is contributed equally to all participating individuals. REFERENCES 1. Turbelin, A., & Catford, J. A. (2021). Invasive plants and climate change. In Climate change (pp. 515-539). Elsevier. DOI: https://doi.org/10.1016/B978-0-12-821575-3.00025-6 2. Wang, Z., Yue, R., & Li, Y. (2021). Research Progress on Growth Characteristics of Invasive Plants in Different Habitats. In E3S Web of Conferences (Vol. 257, p. 03023). EDP Sciences. DOI: https://doi.org/10.1051/e3sconf/202125703023 3. 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He was a member of the Kerala State Biodiversity Board. In this capacity, he has contributed to biodiversity conservation efforts in the state. He was previously an Associate Professor at Government Brennen College, Thalassery, Kannur. He has contributed to research on Kaipad rice farming, a unique saline-resistant organic farming system of North Kerala, as well as on plant genetics and variability. He has published articles in peer-reviewed and significant Journals. Swedha Madhavan M is a Research Scholar, currently doing her PhD (CSIR-SRF) in the Department of Botany, Government Brennen College, Thalassery, Kannur. She obtained her Bachelor of Science (BSc) degree in Botany from Nirmalagiri College, Kuthuparamba, affiliated with Kannur University, and her Master of Science (MSc) degree in Botany from Government Brennen College, Thalassery, also affiliated with Kannur University in 2018. She qualified for the GATE in Life Sciences (2019) and the Joint CSIRUGC NET and JRF in Life Sciences. She has published articles in peer-reviewed Journals. Dr Sreeja P is an Associate Professor and Head of the Department of Botany at Sir Syed College, Taliparamba. An expert in mangrove ecology and biodiversity studies, she holds a PhD on the ecosystem significance and socio-economic impact of mangrove-rich wetlands of North Malabar. She has guided three PhD theses to completion and continues to supervise research scholars. She is actively involved in mangrove restoration programmes, contributing to both research and conservation. She has published articles in peer-reviewed and significant Journals. Dr Sreeja P. has received several recognitions for her academic and conservation contributions. WWF acknowledged her as the Best Volunteer for Mangrove Conservation in South India. In 2022, she was conferred the Prof. M. Muraleedharan Award for Best College Teacher at the state level and won the Best Paper Award for her work on invasive species research at a KSBB national conference. Sharfa Usman is currently pursuing her B.Ed. at Malabar Training College, Peravoor, affiliated with Kannur University. She obtained her Bachelor's degree (BSc) in Plant Science from Pazhassiraja NSS College, Mattannur, affiliated with Kannur University. She received her Master's degree (MSc) in Botany from Sir Syed College, Taliparamba, affiliated with Kannur University. Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of the Lattice Science Publication (LSP)/ journal and/ or the editor(s). The Lattice Science Publication (LSP)/ journal and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions, or products referred to in the content.