Climate Past, Climate Future: A Story of Aquatic Plants


		Search all stories:

	Home \|\| Sections: Fieldwork \| Research \| Outreach \| Meetings \| Awards \| Staff & Center News \| Publications \|\| Archives

Climate Past, Climate Future: A Story of Aquatic Plants

By Beth A. Middleton
August 2009

in this issue:
previous story \| next story

U.S. Geological Survey (USGS) scientists with extensive knowledge of coastal processes occasionally apply their expertise to scientific problems in inland areas. One of these scientists, Beth Middleton of the USGS National Wetlands Research Center in Lafayette, Louisiana, was recently asked to look at the impact of droughts on wetland vegetation in Keoladeo National Park in northern India. This is her story about that work.—Ed.

The biodiversity of some of the world's best national parks may be threatened by water shortages, and predicted climate change could accelerate this problem in the future. The aquatic plant species of national parks in India may be particularly threatened by any future water shortages. According to forecasts for India by the National Centre for Medium Range Forecast (NCMRF), even though there may be 10 percent more rain in the future, temperatures may be 3-5°C hotter, so that water may become less available. The NCMRF also predicts more extreme storm activity. Monsoons—seasonal winds that bring rainfall to the region—are already becoming less predictable. If longer periods of drought occur in northern India in the future, national parks may need to prepare for biodiversity changes, particularly in aquatic plant species.

Above: A gathering of the Keoladeo Naturalists Society, a group of naturalists and rickshaw pullers working in the Keoladeo National Park. Some of the members of this group worked on ecosystem studies with USGS research ecologist Beth Middleton during the 1980s as part of her Ph.D. dissertation work with Iowa State University. [larger version]

Local observers have noted the shrinking of habitat for aquatic plant species in the Keoladeo National Park in Bharatpur, Rajasthan, northern India, after a number of years of drought and upstream water abstraction. The Keoladeo Naturalists Society invited U.S. Geological Survey (USGS) research ecologist Beth Middleton to visit the park to make observations of aquatic species of concern (Technical Assistance Agreement T-09-763b). The Keoladeo Naturalists Society (a.k.a. "The Barefoot Naturalists") is a group of local nature guides and rickshaw pullers. Middleton is a researcher who studies the impact of climate change, drought, and hurricanes on coastal wetlands; because of this expertise, she was asked to look at the impact of droughts on the Keoladeo National Park wetlands. Middleton did her Ph.D. research in India 20 years previously, so she was familiar with the park under conditions of more normal flooding. Upon her return in April 2009, the park looked very different after several years of drought. The aquatic areas of the park appeared to be smaller than during the 1980s; however, at least one positive observation is that park managers have enlisted local villagers to remove the invasive mesquite plant, Prosopis juliflora, within upland savanna habitats .

Above: Keoladeo National Park, India, showing sites (arrows) checked in April 2009 for aquatic plant species of concern, based on the presence of these species (listed in shaded boxes) in seed banks at the sites in the 1980s. Lettered zones are bounded by roads and levees. Blue areas, wetlands; green areas, savanna. [larger version]

Water shortages and drought are predicted for many places in the future as a consequence of climate change, and this story of potential biodiversity loss related to drought in the Keoladeo National Park is instructive for those of us who work to prevent the loss of native species. The Keoladeo Naturalists were concerned that after several years of drought, some aquatic species might now be lost from the park. The 2008 monsoon rains were more nearly normal, so that some of the aquatic habitats filled with water. Accepting the invitation to return to India after 20 years, Middleton spent several days searching drying ponds for aquatic species in April 2009. April is a time of the year during which ponds normally become dry. During a "normal" year in this part of northern India, wetlands dry during the very dry and hot summer (March-June), then fill with water (July-October), and stay wet during a cold winter (November-February).

Above left: Example of aquatic species in Keoladeo National Park: Nymphoides cristata (floating heart). [larger version]

Above right: Example of aquatic species in Keoladeo National Park: Nymphoides indica (water snowflake). [larger version]

Members of the Keoladeo Naturalists Society and Middleton searched the park for aquatic species of concern, but not without some trepidation. Although aquatic species of monsoonal wetlands are adapted to drought, the question arises after many years of continuous drought: how long can aquatic species maintain themselves without water? Middleton suggested that areas of the park be checked where these species of concern had been found as seeds in seed banks (natural accumulations of viable seeds in the soil) studied during the 1980s. By following this strategy, the team found a number of the aquatic species of concern, albeit in restricted abundance on the edges of the drying ponds. The team found species such as Cyperus rotundus, Nymphoides indica, Paspalum distichum, Potamogeton pectinatus, Scirpus tuberosus, and Vallisneria natans.

Above left: Villagers have been cutting the invasive mesquite (Prosopis juliflora) from savanna forest and digging the stumps out by the root. Managers at the Keoladeo National Park hope that eventually this invasive species can be controlled in the park. Native species such as Salvadora oleiodes and Vetiveria zizaniodes survived under the mesquite and are available to revegetate the savanna. In the 1980s, many savanna portions of the park were completely infested with Prosopis juliflora. [larger version]

Above right: Savanna forest after invasive mesquite (Prosopis juliflora) removal. Large tree to left is a kadam, Mitragyna parvifolia. [larger version]

It was good news to discover that many of the aquatic species were still growing in the national park, but questions remain regarding the mechanisms underlying the drying of the park. Factors other than water abstraction, monsoon fluctuation, and climate drying might be contributing to this phenomenon. For example, could the wetland become drier because accumulation of plant matter is raising the ground elevation? Middleton's graduate studies at Iowa State University in the 1980s on the relationships between plant production and decomposition yielded some information regarding the controls of ground elevation in wetlands. Such baseline data are critical to understanding whether current rates of organic filling of wetlands may have changed from 20 years ago, and surface elevation table (SET) elevation analyses are suggested as future studies.

Above: Drying pool in Keoladeo National Park, India, March 12, 2008, with wintering bar-headed geese, migrant sandpipers, and possibly-breeding egrets. The park is highly prized for its populations of water birds, including migratory waterfowl and resident nesting birds. From UNESCO (2.2 MB PDF file). [larger version]

The observations made in April 2009 by Middleton were a pilot study to determine the extent of the problem for aquatic plant species related to drought. Plans are underway for a more extensive vegetation survey in October 2009 to determine if the abundances of these species of concern have changed in the past 20 years. But this analysis can only occur if the monsoon of 2009 cooperates and fills the temporary ponds of the Keoladeo National Park.