The water-loving evergreen tree, hijol, adapted to floodplains, has been traditionally managed over millennia as family and community forest in the Ganges-Brahmaputra-Meghna basin. A new study that works out the impact of climate change notes that the species distribution will be hit by erratic rainfall and temperature changes.

The suitable habitat for hijol (Barringtonia acutangula) to grow in the India-Bangladesh landscape may shrink by 50.5% due to rainfall and temperature changes, the study, which models current and future climate scenarios, predicts. The authors recommend that the International Union for Conservation of Nature assess the species vulnerability and list it in its assessment.

“We chose Barringtonia acutangula for our study because of its socioeconomic importance among floodplain farmers. The primary vocation of the floodplain farmer is fish farming. The use of Barringtonia is intricately related to fish farming in Assam, which is why the species is so important to study for its conservation,” Arun Jyoti Nath at the Department of Ecology and Environmental Science, Assam University and the corresponding author of the study told Mongabay India.

The branches of the trees are used in fisheries to check for predators as the network of branches provide hiding spaces for the fish during threats by predators. Complex branches hinder illegal fishing by other fishermen as well. Additionally, the rough branch surface is conducive to grow algae.

Barringtonia acutangula grows on banks of the river, edges of freshwater swamps and lagoons and seasonally-flooded lowland plains, where often it is the dominant species, from the sea level up to about 400 metres of altitude.

Hijol in Son Beel in southern Assam. Credit: Arun Jyoti Nath

The tree is widely distributed throughout Southeast Asia, Australia and Africa. The species is found in the floodplains of the Indo-Bangladesh landscape which is cradled by the Ganges-Brahmaputra-Meghna basin.

Nath and co-authors said the low-lying floodplain areas of the Indo-Bangladesh landscape are suitable habitats for B acutangula. Erratic rainfall in the region may alter the floodplain system’s functioning and affect the distribution of Barringtonia forest on local, regional and global scales, they said.

Like other floodplain tree species, hijol disperses its seed during the flooding season. Seed germination rate is strongly influenced by seed mass and sufficient moisture content in producing better seedlings.

“The floodplain areas are the most vulnerable ecosystems to climate change; the vulnerability has been exacerbated by erratic rainfall and increased variability in temperature and evaporation. In addition, climate change can affect the floodplain forest ecosystems by reducing forest cover, causing biodiversity loss and altering species distribution,” Nath said.

Ecologist Abhik Gupta who was not associated with the study, observed that hijol could be seen as a ‘signature’ species of these floodplains. “Any attempt, therefore, to chart the possible impact of climate change on this species that inhabits a very important habitat zone in the Indian subcontinent, carries sufficient significance,” Gupta at Assam University told Mongabay-India.

“In this sense, the study is serving as an indicator of the tough challenges that climate change is throwing – which are likely to be intensified in the coming years – to the human inhabitants, the biodiversity, and ecosystem integrity and stability of the highly productive yet fragile floodplain landscapes of the Ganges-Brahmaputra-Meghna basin,” added Gupta.

The study found that of the total area, i.e., 24,50,577 sq km, of the Indo-Bangladesh landscape, 1,99,063 sq km (8.12%) is highly suitable for the distribution of B acutangula, but is likely to shrink by 50.5% (100,669 sq km) by 2050 due to climate change impacts.

Country-wise habitat analysis revealed that out of the total area (1,39,799 sq km) in Bangladesh, 95,541 sq km (68.3%) is a highly suitable area for B acutangula, but this is projected to decline by 34,801 sq km (36.4%) by 2050 due to climate change. In India, the highly suitable area of B acutangula is 1,03,522 sq km (4.48%) and may decline by 65,868 sq km (63.6%) by 2050, the scientists project.

The branches of Barringtonia acutangula are used in fishery management. The network of branches provides fish protection from predators. Credit: Arun Jyoti Nath

Study co-author Jyotish Ranjan Deka of the Wildlife Institute of India said the species is known for its multiple uses and ecosystem benefits. “Since the species is not in the International Union for Conservation of Nature assessment, their range is rapidly declining. We recommended International Union for Conservation of Nature to assess their vulnerability and list under assessment,” he told Mongabay-India.

“We have identified 89 current locations from the Indo-Bangladesh landscape that can be included in the International Union for Conservation of Nature Red List assessment report for B acutangula in the future. Currently, only two occurrence points have been included in the International Union for Conservation of Nature assessment report from the India-Bangladesh landscape. Inclusion of these locations will enable us to know the existing distribution of the species and help to get global attention to the effective management of the species,” Animekh Hazarika, study co-author, told Mongabay-India.

Floodplain systems are often misused as dumping grounds of municipal waste, setting up industries, conversion to agricultural land, etc., which has led to the demolishing of floodplains at an alarming rate, notes the study. “Human intervention distorts the natural services of the floodplain and severely influences the floodplain dwellers in multidimensional ways. In this context, floodplain Barringtonia forest management is crucial to sustaining the floodplain farmers’ livelihood,” the study said.

Navendu Page, a scientist at the Wildlife Institute of India who is not associated with the study, expressed doubts about the habitat decline estimates of hijol. “Also, they have missed out on many occurrence locations from the western part of South India, and hence their predicted distribution may not reflect the full set of environmental or climatic conditions that the species can survive. Finally, species may also show resilience to changing climate, which is hard to predict if the suitable habitat may increase or decrease,” he said.

Natural resource management expert HM Tuihedur Rahman, who has worked on understanding climate change impacts on the swamp forests of Bangladesh, including Barringtonia acutangula, called for collaborative management actions for conserving the species between India and Bangladesh. “Particularly, upland forest destruction (i.e., in Assam and Meghalaya) causes huge erosion and the resulting silt and sand is carried by the rivers to the wetlands (wetlands are the depressions where water retains during monsoon and dries up during dry season, although there might be some permanent inundation areas in a wetland),” said Rahman, at the Department of Agricultural and Resource Economics, University of Saskatchewan, Canada.

“This is one of the main causes of wetland loss in Bangladesh. A joint intervention might help erosion reduction to help solve the siltation problem. Also, transboundary river management is one of the main political issues yet unresolved between the countries, which is an underlying factor for poor management. Both countries can share information and develop shared plans and expertise for the conservation efforts,” Rahman, who was not associated with the study, told Mongabay-India.

This article first appeared on Mongabay.