Plants picked up to 150 years ago by Victorian collectors and held by the million in herbarium collections across the world could become a powerful – and much needed – new source of data for studying climate change, according to research published this week in the British Ecological Society's Journal of Ecology.
The scarcity of reliable long-term data on phenology – the study of natural climate-driven events such as the timing of trees coming into leaf or plants flowering each spring – has hindered scientists' understanding of how species respond to climate change.
But new research by a team of ecologists from the University of East Anglia (UEA), the University of Kent, the University of Sussex and the Royal Botanic Gardens, Kew shows that plants pressed up to 150 years ago tell the same story about warmer springs resulting in earlier flowering as field-based observations of flowering made much more recently.
The team examined 77 specimens of the early spider orchid (Ophrys sphegodes) collected between 1848 and 1958 and held at the Royal Botanic Gardens, Kew and the Natural History Museum in London. Because each specimen contains details of when and where it was picked, the researchers were able to match this with Meteorological Office records to examine how mean spring temperatures affected the orchids' flowering.
They then compared these data with field observations of peak flowering of the same orchid species in the Castle Hill National Nature Reserve, East Sussex from 1975 to 2006, and found that the response of flowering time to temperature was identical both in herbarium specimens and field data. In both the pressed plants and the field observations, the orchid flowered 6 days earlier for every 1oC rise in mean spring temperature.
The results are first direct proof that pressed plants in herbarium collections can be used to study relationships between phenology and climate change when field-based data are not available, as is almost always the case.
According to the study's lead author, PhD student Karen Robbirt of UEA: "The results of our study are exciting because the flowering response to spring temperature was so strikingly close in the two independent sources of data. This suggests that pressed plant collections may provide valuable additional information for climate-change studies."
"We found that the flowering response to spring temperature has remained constant, despite the accelerated increase in temperatures since the 1970s. This gives us some confidence in our ability to predict the effects of further warming on flowering times."
The study opens up important new uses for the 2.5 billion plant and animal specimens held in natural history collections in museums and herbaria. Some specimens date back to the time of Linnaeus (who devised our system of naming plants and animals) 250 years ago.
Co-author Professor Anthony Davy of UEA says: "There is an enormous wealth of untapped information locked within our museums and herbaria that can contribute to our ability to predict the effects of future climate change on many plant species. Importantly it may well be possible to extend similar principles to museum collections of insects and animals."
Phenology – or the timing of natural events – is an important means of studying the impact of climate change on plants and animals.
"Recent climate change has undoubtedly affected the timing of development and seasonal events in many groups of organisms. Understanding the effects of recent climate change is a vital step towards predicting the consequences of future change. But only by elucidating the responses of individual species will we be able to predict the potentially disruptive effects of accelerating climate change on species interactions," he says.
Detecting phenological trends in relation to long-term climate change is not straightforward and relies on scarce long-term studies. "We need information collected over a long period to enable us confidently to identify trends that could be due to climate change. Unfortunately most field studies are relatively brief, so there are very few long-term field data available," Professor Davy explains
The new analysis, which has been undertaken for World Water Week, identifies that the worrying decline in many of the world's turtle species is evidence that humanity's management of vital freshwater ecosystems is causing deep and damaging environmental impacts that will affect people and wildlife alike.
Dr Peter Paul van Dijk, Director of Conservation International's Tortoise and Freshwater Turtle Conservation Program said: "The key problems these animals are facing are changes to their habitats – in particular because of the damming of the rivers where they live for hydro-electricity, on top of hunting for food and a very lucrative trade in rare turtles as pets.
"More than 40 percent of the planet's freshwater turtle species are threatened with extinction – making them among the most threatened groups of animals on the planet. Their decline is an indicator that the freshwater ecosystems that millions of people rely on for irrigation, food and water are being damaged in a manner that could have dire consequences for people and turtles alike."
The analysis identifies a number of turtle species that are particularly threatened, and Dr van Dijk has listed ten he considers are severely at risk (images are available from the link below):
Red River Giant Softshell Turtle, Rafetus swinhoei – With only four individuals remaining alive in the world, this may be the most threatened of all turtles. Two long-term captive animals in China were brought together three years ago and have produced eggs, but these failed to develop. One lone animal confined in Hoan Kiem lake in downtown Hanoi is revered as symbol of Vietnam's independence. And the last animal remaining in the wild – also in Vietnam – became the reluctant subject of a hostage drama when his home reservoir burst its dam in November 2008, was washed downriver, and was caught by a fisherman who only released it back to conservationists after protracted negotiations; the day ended well for all involved, particularly the turtle who was released back into its native wetland late that night.
Red-crowned River Turtle Batagur kachuga,– historically widespread throughout the great rivers of northern India, Bangladesh and Nepal, intensive egg collection, capture of adults for consumption, dams, and river pollution impacted it so badly that there's only a single viable population left, in the 'unholy' Chambal River of central India. Males remain much smaller than females and colour spectacularly for courtship season.
Myanmar River Turtle Batagur trivittata,– 'Sibling species' of the B. kachuga, feared extinct from 1935 until rediscovery in 1993, this species once occurred in large numbers in the Irrawaddy river system of Myanmar (Burma) until its populations shrunk to under a dozen mature animals in the upper Chindwin river as a result of egg collection, hunting and habitat degradation including dams and gold mining. The eggs of these last animals have been protected in recent years and the juveniles are being raised at Mandalay Zoo for re-introduction.
Roti Snake-necked Turtle Chelodina mccordi,– discovered on the small Indonesian island of Roti in 1994, it was immediately in great demand for the pet trade in America, Europe and Japan, and the species was collected into near-extinction by 2000. Captive breeding for re-introduction is slow and a long-term prospect at best.
Southeast Asian Giant Softshell Turtle Chitra chitra,– One of the largest turtles in the world (weighing up to a quarter ton), it is restricted now to scattered individuals in two rather small rivers in western Thailand and Java (Indonesia), where they continue to be under severe threat from hunting for consumption, egg collection, and pollution and damming of these rivers.
Yunnan Box Turtle Cuora yunnanensis,– considered extinct until a few individuals were found in 2005 at a location still kept secret in China's Yunnan province, these animals are the nucleus of a hoped-for conservation breeding program for the species. Black market prices in the pet trade may exceed USD 10,000.
Central American River Turtle Dermatemys mawii– a big, vegetarian turtle, primarily found in Mexico, Guatemala and Belize, the last species of a group that traces its ancestry back to the time of the dinosaurs, with no obvious changes in appearance. Its meat is highly prized in Central America for Lent, Easter and other religious celebrations, making it so valuable that collectors charter planes to fly into remote wetlands, collect these turtles, and fly them out.
Bog Turtle Glyptemys muhlenbergii, – A tiny (4 inch shell length) turtle of the foothills of the Eastern USA, it is a habitat specialist living in spring meadows and other small marshes, where it digs tunnels like a mole to hunt for worms, slugs and grubs. About 98 percent of its habitat has been converted to agricultural lands, with just scattered small populations remaining from New York to Tennessee.
Annam Pond Turtle Mauremys annamensis,– a species restricted to marshy wetlands of central Vietnam, it was intensively collected to supply the Chinese food trade in the 1990s and only a handful of animals remain in the wild. There are good populations in captivity, which breed well, and repatriation to Vietnam as a first step towards re-introduction of the species has already occurred.
Coahuila Box Turtle Terrapene coahuila,– All other box turtles (so named because the two halves of the lower shell can raise up and close off the shell like a box) are mostly land-living, but this species from the semi-desert of northern Mexico has gone back to living permanently in freshwater – in its case the springs and marshes of Cuatro Cienegas, a desert oasis complex under significant threat from desiccation through groundwater pumping for agriculture and residential use, as well as agricultural land conversion within the Cuatro Cienegas basin.
IN PHOTOS: See these turtles in our Endangered Turtles photo gallery.
Dr. Tracy Farrell, the leader of Conservation International's Freshwater team added: "It's time that the international community recognized that we need a holistic approach to managing our freshwater ecosystems. Failure to protect the source, flow and delivery of freshwater in an interconnected way, results in a loss of benefits to species and people. We have already lost half of our wetlands and dammed two thirds of our major rivers . Damming in one place can have dramatic consequences downstream, and if we don't consider the whole of a system we threaten not only important populations of animals – like turtles – but also human populations that rely on these waterways for food, irrigation, drinking water and even transport."
Peter Paul van Dijk added: "If we don't act now to protect the habitats that support these creatures and take stronger action to tackle both the international and domestic markets in these animals for pets and food we stand a very real chance that we will lose them forever."
IN DEPTH: Learn more about freshwater turtles.
"Bee numbers may have declined at our research site, but we suspect that a climate-driven mismatch between the times when flowers open and when bees emerge from hibernation is a more important factor," says James Thomson, a scientist with U of T's Department of Ecology and Evolutionary Biology.
Thomson's 17-year examination of the wild lily in the Rocky Mountains of Colorado is one of the longest-term studies of pollination ever done. It reveals a progressive decline in pollination over the years, with particularly noteworthy pollination deficits early in the season. The study will be published in Philosophical Transactions of the Royal Society B: Biological Sciences on September 6.
Three times each year, Thomson compared the fruiting rate of unmanipulated flowers to that of flowers that are supplementally pollinated by hand. "Early in the year, when bumble bee queens are still hibernating, the fruiting rates are especially low," he says. "This is sobering because it suggests that pollination is vulnerable even in a relatively pristine environment that is free of pesticides and human disturbance but still subject to climate change."
Thomson began his long-term studies in the late 1980s after purchasing a remote plot of land and building a log cabin in the middle of a meadow full of glacier lilies. His work has been supported by the U.S. National Science Foundation and the Natural Sciences and Engineering Research Council of Canada.
