Posts Tagged ‘science & environment’
Source: (bbc.co.uk)
By Paul Rincon
Science reporter, BBC News
Scientists have identified a previously unknown type of ancient human through analysis of DNA from a finger bone unearthed in a Siberian cave.
The extinct "hominin" (humanlike creature) lived in Central Asia between 48,000 and 30,000 years ago.
An international team has sequenced genetic material from the fossil showing that it is distinct from that of Neanderthals and modern humans.
Details of the find, dubbed "X-woman", have been published in Nature journal.
Professor Chris Stringer, human origins researcher at London's Natural History Museum, called the find "a very exciting development".
"This new DNA work provides an entirely new way of looking at the still poorly-understood evolution of humans in central and eastern Asia."
The discovery raising the intriguing possibility that three forms of human - Homo sapiens, Neanderthals and the species represented by X-woman - could have met each other and interacted in southern Siberia.
Origin unknown
The tiny piece of finger bone was uncovered by archaeologists working at Denisova Cave in Siberia's Altai mountains in 2008. An international team of researchers extracted mitochondrial DNA from the bone and compared the genetic code with those from modern humans and Neanderthals.
Mitochondrial DNA comes from the cell's powerhouses and is passed down the maternal line only. The analysis carried out by Johannes Krause from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and colleagues revealed the human from Denisova last shared a common ancestor with humans and Neanderthals about one million years ago.
This is known as the divergence date: essentially, when this human's ancestors split away from the line that eventually led to Neanderthals and ourselves.
The Neanderthal and modern human evolutionary lines diverged much later, around 500,000 years ago. This shows that the individual from Denisova is the representative of a previously unknown human lineage that derives from a hitherto unrecognised migration out of Africa.
"Whoever carried this mitochondrial genome out of Africa about a million years ago is some new creature that has not been on our radar screens so far," said co-author Professor Svante Paabo, also from the Max Planck Institute for Evolutionary Anthropology.
The divergence date of one million years is too young for the Denisova hominin to have been a descendent of Homo erectus, which moved out of Africa into Asia some two million years ago.
And it is too old to be a descendent of Homo heidelbergensis, another ancient human thought to have originated around 650,000 years ago.
Slice of time
The research contributes to a more complex emerging picture of humankind during the Late Pleistocene, the period when modern humans left Africa and started to colonise the rest of the world.
Professor Clive Finlayson, director of the Gibraltar Museum, has previously argued that "a time slice at a point in the late Pleistocene would reveal a range of human populations spread across parts of Africa, Eurasia and Oceania.
"Some would have been genetically linked to each other, behaving as sub-species, while the more extreme populations may well have behaved as good species with minimal or no interbreeding."
It was long known that modern humans may have overlapped with Neanderthals in Europe for more than 10,000 years. But in 2004, researchers discovered that a dwarf species of human, dubbed "The Hobbit", was living on the Indonesian island of Flores until 12,000 years ago - long after modern humans had colonised the area.
Neanderthals appear to have been living at Okladnikov Cave in the Altai mountains some 40,000 years ago. And a team led by Professor Anatoli Derevianko, from the Russian Academy of Sciences, has also found evidence of a modern human presence in the region at around the same time.
Professor Stringer commented: "Another intriguing question is whether there might have been overlap and interaction between not only Neanderthals and early moderns in Asia, but also, now, between either of those lineages and this newly-recognised one."
"The distinctiveness of the mitochondrial DNA patterns so far suggests that there was little or no interbreeding, but more extensive data will be needed from other parts of the genome, of from the fossils, for definitive conclusions to be reached."
Paul.Rincon-INTERNET@bbc.co.uk
This article is from the BBC News website.
Source: (bbc.co.uk)
Researchers have discovered a nearly complete fossil of a dinosaur which appears to have been caught in a collapsing sand dune.
The Seitaad ruessi fossil, described in the journal PLoS ONE, is a relative of the long-necked sauropods that were once Earth's biggest animals.
S. ruessi, found in what is now Utah, could have walked on all four legs, or risen up to walk on just two.
It is from the Early Jurassic period, between 175 and 200 million years ago.
At that time, all of Earth's continents were still joined in the super-continent Pangaea, and sauropodomorphs like S. ruessi have been found in South America and Africa.
Unlike the sauropods to which they are related, S. ruessi was relatively small, about a metre tall and 3.5-4m long with its lengthy neck and tail, weighing in at between 70 and 90kg.
Plant life
Much of the fossil, first discovered by a local artist in 2004, was perfectly preserved in sandstone. However, it is missing its head, neck and tail.
Joseph Sertich of the University of Utah and Mark Loewen from the Utah Museum of Natural History then worked to free S. ruessi from its sandy grave - in an arid part of the US that, 185 million years ago, formed part of a huge desert.
"Although Seitaad was preserved in a sand dune, this ancient desert must have included wetter areas with enough plants to support these smaller dinosaurs and other animals," said Mr Sertich.
"Just like in deserts today, life would have been difficult in Utah's ancient 'sand sea.'"
This article is from the BBC News website.
Source: (bbc.co.uk)
VIEWPOINT
Mark Chandler
The interests of farmers are often perceived to be in conflict with those of both the ecosystems and the markets in which they operate, says Mark Chandler. In this week's Green Room, he argues that ongoing, directed efforts can create profitable, sustainable situations for everyone.
"Rather than seeing the use and development of agricultural lands as the conversion of natural systems into human-dominated ones, there are increasing opportunities for win-win solutions"
Fuelling the growing demand for food, fuel and fibre, 13 million hectares are converted annually for agricultural use, mostly from forests.
Together, crops and pasture make up more than any other land use - over 40% - and are projected to grow by another 15% over the next 50-100 years.
The conversion into agricultural lands is perhaps one of the greatest single impacts on the Earth. These impacts include the greenhouse gas emissions that make up a third of global emissions since 1950, the 70% of freshwater used for irrigation, and growing loss of biodiversity, among others.
The use of the planet's resources is no longer sustainable. A recent study by WWF, the Zoological Society of London and the Global Footprint Network revealed that humans now use in excess of 25% of the productive capacity of the biosphere and that two planet Earths will be needed to support our projected demand.
The scope and scale of agriculture and the projected growth in demand for food, biofuels and other commodities puts it on a crash course with identified pathways for environmental sustainability.
With a growing awareness of the value of the goods and services that nature provides, governments and institutions are looking for ways to both decrease per capita demand and increase the efficiency of current land use practices.
But how can agricultural landscapes produce more with less impact
Coffee wake-up
While the interests of farmers are often seen to be at odds with others in the supply chain, a dialogue is taking place about ways to build on shared interests across the global supply chain. Creating dialogue across sectors that typically do not interact in this way has led to some interesting advances.
Critical to success is our ability to define how to pay for the costs of maintaining the goods and services, and who pays. Incentives are evolving, including certification standards such as Fair Trade and the newly developing payments for ecosystem services like those for water, or the trading of carbon.
Developing our understanding of the relationships and trade-offs among forests, soil, biodiversity, water, and food production among other key ecosystem components is driving a new paradigm for applied scientific research.
So are there interventions that can create win-win situations for both land owners and the regional community at large Two examples from the world of sustainable coffee production follow.
Coffee is one of the top five traded global commodities. A hundred million people depend on it for their livelihoods and the evolving models provide insight into the opportunities and challenges for sustainable agriculture.
Pollinating insects help with the production of over 65% of the world's crops. Recent declines in native and managed bee colonies have created concern about food production.
An ongoing project by Earthwatch illustrates the connection of these pollinators to the landscape and how different stakeholders come together to identify potential solutions.
A recent research project by Valerie Peters from the University of Georgia in the US, using teams of Earthwatch volunteers, found that wild and domesticated bees enhanced both the yield and quality of coffee berries near Monteverde, Costa Rica.
Wild bees and other pollinators were in turn attracted by plants, other than coffee, which the farmers had grown around their fields. Recognising the value of these other management practices in boosting yields helps farmers understand the benefits of biodiversity in the landscape.
Citizen science
Dr John Banks of the University of Washington Tacoma in the US and Earthwatch are expanding on this work in the Tarrazu coffee region of Costa Rica.
Working with farmers, volunteers from organisations such as Starbucks Coffee Company and the accounting and advisory firm Ernst & Young LLP, are identifying the value of nearby forests in boosting bee populations and coffee production.
These volunteers and other citizen scientists are helping to collect and analyse field data as it relates to bee activity and coffee plant growth.
These diverse teams of volunteers are also exploring the financial mechanisms that help recognise and reward the goods and services that farmers and forests provide to local and global communities.
Ernst & Young LLP volunteers in particular will assist the Costa Rican cooperative managers in their effort to improve their business practices and develop better pricing structures for sustainable coffee production.
While the increase in intensive agriculture and the use of fertilisers and pesticides has produced dramatic increases in yield, this has come at the cost of degraded habitats, particularly the soil.
New sustainable techniques are needed to mitigate the negative consequences of intensive agriculture. Rebuilding healthy, diverse soils requires great effort to yield not only nutritional, healthy food, but also to mitigate erosion, capture carbon, and act as a sponge to prevent flooding, among other benefits.
Providing farmers with ways to enhance their soils for these diverse benefits takes a multi-sectoral approach. By engaging local organisations and Starbucks employees, Earthwatch is finding that useful tools can be developed that benefit farmers.
In Costa Rica, like much of the world, there is a need to protect against practices that acidify the soils, and rebuild their organic matter and thus natural capital. The linking of research with both ends of the supply chain is enhancing the uptake of better soil conservation measures.
Rather than seeing the use and development of agricultural lands as the conversion of natural systems into human-dominated ones, there are increasing opportunities for win-win solutions. Rural farming communities are among the poorest on Earth, yet they are often open to change - and have much to lose otherwise.
Adoption by consumers, governments and businesses of financial mechanisms such as certification and payment for ecosystem services is needed to ensure that the cost burden by producers of enhancing the environment is adequately compensated.
Solutions to address this challenge are being drafted through unlikely collaborations - consumers, farmers, corporations and governments. Learning and trust across this global community is essential.
Mark Chandler is international director of research for the Earthwatch Institute; he spoke at the Earthwatch lecture "Farming and Sustainable Environments" on 17 March, available as a podcast
The Green Room is a series of opinion articles on environmental topics running weekly on the BBC News website
Do you agree with Dr Chandler Can these examples of "win-win" situations be scaled up to a whole world full of conflicting agricultural and environmental interests Is there any hope in maintaining "natural capital" in the face of a rising population with exponentially higher needs
Send us your comments using the form below:
This article is from the BBC News website.
Source: (bbc.co.uk)
By Paul Rincon
Science reporter, BBC News
Immense volcanic activity helped the dinosaurs rise to prominence some 200 million years ago, a study suggests.
Dinosaurs were the dominant vertebrates on land for some 160 million years.
While it is widely accepted that an asteroid or comet wiped them out, there has been less agreement on the factors which led to their ascendancy.
Research in PNAS journal suggests volcanic eruptions changed the climate, causing a mass extinction that wiped out the dinosaurs’ main competitors.
The scientific paper, by researchers from the US and Taiwan, looked at several lines of evidence such as plant lipids and wood from sediments interbedded with lava flows.
These flows are dated to the end-Triassic extinction, which wiped out 50% of tetrapods (four-limbed animals) on land, 50% of terrestrial plants and 20% of marine families.
The scientists examined how two different isotopes (or forms) of carbon fluctuated during these volcanic eruptions. They found that the “heavy” form of carbon was depleted relative to the “light” form.
Super greenhouse
They say this reflects disturbances in the carbon cycle at this time, including a spike in atmospheric carbon dioxide (CO2) and aerosols (fine solid particles).
This would have resulted in “super” greenhouse warming, according to lead author Jessica Whiteside, a geologist at Brown University in Providence, Rhode Island.
“We are showing that these events are synchronous with the extinction and that the events all occur within a few tens of thousands of years of the eruption of these huge lava flows,” Dr Whiteside told BBC News.
The scientists have not yet determined the killing mechanism.
Neither can they say for sure why the dinosaurs survived, although Dr Whiteside suggests it could have been “blind luck”.
Nevertheless, they propose that the climatic catastrophe caused by the mass eruptions led to the extinction of the dinosaurs’ main competitors, the crurotarsans.
These ancient crocodile-like creatures had competed vigorously with early dinosaurs during the Triassic Period.
The study is not the first to posit a link between volcanic activity and the end-Triassic mass extinction.
But the relationship between volcanism, carbon isotope anomalies and extinctions had never been tested in rocks preserving records of all three phenomena. The scientists say this is the first study to do so.
Big break-up
The so-called volcanic “flood basalts” form a giant geological entity known as the Central Atlantic Magmatic Province (Camp).
This was formed during the break up of the “supercontinent” known as Pangaea, causing lava to pour out on to the Earth’s surface for some 700,000 years.
“This is actually the largest flood basalt province known in the Solar System. It covers something like 9-11 million sq kilometres. To give you an indication of how large that is, it’s about one-third the size of the Moon,” said Dr Whiteside.
“We’re talking about a serious amount of the Earth being covered in lava.”
It dwarfs the Deccan traps, a large igneous province in west-central India. The volcanism which created the traps had been implicated by some in the extinction of the dinosaurs 65 million years ago.
Earlier this month, a panel of experts strongly endorsed evidence that a space impact was instead responsible for this extinction.
Writing in Science journal, they ascribed the cause to a 10-15km space rock striking the Yucatan Peninsula. This caused a global winter that played havoc with marine and land ecosystems.
Paul.Rincon-INTERNET@bbc.co.uk
This article is from the BBC News website.
Source: (bbc.co.uk)
By Paul Rincon
Science reporter, BBC News
Immense volcanic activity helped the dinosaurs rise to prominence some 200 million years ago, a study suggests.
Dinosaurs were the dominant vertebrates on land for some 160 million years.
While it is widely accepted that an asteroid or comet wiped them out, there has been less agreement on the factors which led to their ascendancy.
Research in PNAS journal suggests volcanic eruptions changed the climate, causing a mass extinction that wiped out the dinosaurs' main competitors.
The scientific paper, by researchers from the US and Taiwan, looked at several lines of evidence such as plant lipids and wood from sediments interbedded with lava flows.
These flows are dated to the end-Triassic extinction, which wiped out 50% of tetrapods (four-limbed animals) on land, 50% of terrestrial plants and 20% of marine families.
The scientists examined how two different isotopes (or forms) of carbon fluctuated during these volcanic eruptions. They found that the "heavy" form of carbon was depleted relative to the "light" form.
Super greenhouse
They say this reflects disturbances in the carbon cycle at this time, including a spike in atmospheric carbon dioxide (CO2) and aerosols (fine solid particles).
This would have resulted in "super" greenhouse warming, according to lead author Jessica Whiteside, a geologist at Brown University in Providence, Rhode Island.
"We are showing that these events are synchronous with the extinction and that the events all occur within a few tens of thousands of years of the eruption of these huge lava flows," Dr Whiteside told BBC News.
The scientists have not yet determined the killing mechanism.
Neither can they say for sure why the dinosaurs survived, although Dr Whiteside suggests it could have been "blind luck".
Nevertheless, they propose that the climatic catastrophe caused by the mass eruptions led to the extinction of the dinosaurs' main competitors, the crurotarsans.
These ancient crocodile-like creatures had competed vigorously with early dinosaurs during the Triassic Period.
The study is not the first to posit a link between volcanic activity and the end-Triassic mass extinction.
But the relationship between volcanism, carbon isotope anomalies and extinctions had never been tested in rocks preserving records of all three phenomena. The scientists say this is the first study to do so.
Big break-up
The so-called volcanic "flood basalts" form a giant geological entity known as the Central Atlantic Magmatic Province (Camp).
This was formed during the break up of the "supercontinent" known as Pangaea, causing lava to pour out on to the Earth's surface for some 700,000 years.
"This is actually the largest flood basalt province known in the Solar System. It covers something like 9-11 million sq kilometres. To give you an indication of how large that is, it's about one-third the size of the Moon," said Dr Whiteside.
"We're talking about a serious amount of the Earth being covered in lava."
It dwarfs the Deccan traps, a large igneous province in west-central India. The volcanism which created the traps had been implicated by some in the extinction of the dinosaurs 65 million years ago.
Earlier this month, a panel of experts strongly endorsed evidence that a space impact was instead responsible for this extinction.
Writing in Science journal, they ascribed the cause to a 10-15km space rock striking the Yucatan Peninsula. This caused a global winter that played havoc with marine and land ecosystems.
Paul.Rincon-INTERNET@bbc.co.uk
This article is from the BBC News website.
Source: (bbc.co.uk)
By Jonathan Amos
Science correspondent, BBC News
A Belgian, two Frenchmen and a Colombian-Italian have agreed to be locked away in steel containers for 18 months to simulate a mission to Mars.
Their self-imposed exile will test the physical and mental requirements of ultra-long duration spaceflight.
The Europeans will join a predominantly Russian crew for the Mars500 project, which is due to start in May.
All the food and water needed for the "journey" will have to be loaded into the "spacecraft" before "departure".
There will even be a simulated landing.
After about 250 days, the crew will be split in two and three "cosmonauts" will move into a separate container to walk on the "surface of the Red Planet" wearing modified Russian Orlan spacesuits.
"Mars is the ultimate destination"
Simonetta Di Pippo, Esa director of human spaceflight
"I think you've got to be a little bit crazy to undertake this venture, but it's a healthy craziness," said Diego Urbina, a 26-year-old electronic engineer from Italy.
"I will definitely miss my family and friends, and Nature itself - all the things we take for granted here on Earth, such as the internet. And girls - that's something I'll definitely miss," he told BBC News.
Urbina joins the Belgian Jerome Clevers and the Frenchmen Arc'hanmael Gaillard and Romain Charles as the European Space Agency (Esa) candidates on the project. Their number will shortly be reduced to two.
The selected pair will then join three Russians and a Chinese individual in the simulation spacecraft.
The experiment is being run by Russia's Institute of Biomedical Problems (IBMP) with the key participation of Esa.
The Mars500 facility, which is located on the IBMP site in Moscow, comprises four sealed modules. The total interior volume is about 550 cubic metres. There are no windows.
The walls in the living quarters have been covered with a wooden panelling to make them feel slightly less austere.
Looking after the participants' needs will be a mission control-room sited just outside the containers.
But the experiment's designers are determined to make the training exercise as realistic as possible, so they will introduce a time delay in communications after two months.
Because it can take about 20 minutes for a message to travel from Mars to Earth, it will take this amount of time in the simulation also.
Message delay
The crew and their ground controllers will send text messages to each other and then have to wait for the replies.
It means there can be no real-time conversations with friends and family - and, in moments of crisis, it will mean the crew will have to make crucial decisions themselves.
"Daily life, I hope, will be quite busy," said Romain Charles. "First, when we wake up, we will do some medical checks; and from there we'll all go to different tasks from cooking to cleaning and experiments. And we'll have some spare time to maybe read or watch videos or write to our relatives."
Martin Zell heads up the International Space Station (ISS) utilisation department at Esa. He believes the Mars500 experience will be extremely testing.
"It is literally isolated compared to ISS where you have a lot of arriving and departing vehicles, and at least three of the crew being exchanged every two or four months at least.
"[On the ISS,] you have basically unlimited contact with the ground and you always have new experiments. Whereas on the Mars simulation, you will depart with a certain set of experiments, consumables and equipment - and the door never opens."
Global challenge
The organisers say that if a crew-member decides halfway through the simulation that they really cannot cope with the isolation anymore and want to leave, they will be allowed to so; although every effort will be made to try to persuade them to stay.
The Mars500 is so called because it simulates the duration of a possible human Mars mission in the future using conventional propulsion: 250 days for the trip to the Red Planet, 30 days on the martian surface and 240 days for the return journey, totalling 520 days (in reality it would probably take a lot longer than this).
"Mars is the ultimate destination where we will one day live and work," said Simonetta Di Pippo, the director of human spaceflight at Esa.
"What we're doing right now is working with 13 other space agencies. We have put together a framework for future global endeavour because it's clear this challenge cannot be undertaken by one nation alone. It is, by definition, a global challenge."
It will not happen for many decades, however. The technology does not currently exist to send people to Mars and bring them home safely.
In recent months, the Americans have talked about a "flexible path" out into the Solar System. This would involve sending humans to targets that are progressively further away and more challenging. These targets might include a return to the Moon and visits to asteroids.
Jonathan.Amos-INTERNET@bbc.co.uk
This article is from the BBC News website.
Source: (bbc.co.uk)
The UN's wildlife trade organisations have turned down Tanzania's and Zambia's requests to sell ivory amid concern about elephant poaching.
The countries asked the Convention on International Trade in Endangered Species (CITES) meeting to permit one-off sales from government stockpiles.
The ivory trade was banned in 1989, but three sales have since been granted to nations showing effective conservation.
A Kenyan proposal to ban all such sales in future years was also defeated.
Most conservation groups were delighted that the Tanzanian and Zambian bids were turned down.
But they argue that illegal poaching is the main issue facing African elephants, rather than the occasional legal sale.
"Poaching and illegal ivory markets in central and western Africa must be effectively suppressed before any further ivory sales take place," said Elisabeth McLellan, species programme manager with WWF International.
The meeting in Doha, Qatar also turned down a bid to ban trade in red and pink corals from the Mediterranean Sea.
This article is from the BBC News website.
Source: (bbc.co.uk)
A chairman has been appointed to an independent review into the science published by the research unit at the centre of the "Climategate" row.
Lord Oxburgh is a former chairman of the House of Lords Select Committee on Science and Technology.
"The shadow hanging over climate change and science more generally at present makes it a matter of urgency that we get on with this assessment," he said.
The Lord's appointment was made on the recommendation of the Royal Society.
This is the second independent review into the Climategate e-mail controversy and will scrutinise the published science of the Climate Research Unit (CRU) at the University of East Anglia (UEA).
This is distinct from the panel chaired by Sir Muir Russell which will, amongst other things, examine e-mail exchanges leaked from the unit to determine whether there is evidence of suppression or manipulation of data at odds with acceptable scientific practice.
The e-mails issue came to light in November last year, when hundreds of messages between scientists at the CRU and their peers around the world were posted on the world wide web, along with other documents.
This article is from the BBC News website.
Source: (bbc.co.uk)
VIEWPOINT
Matthew Cock
Europe is about to release its first non-native "biological control" species to curb the spread of Japanese knotweed, and about time too, says scientist Dr Matthew Cock. In this week's Green Room, he sets out the case in favour of introducing natural predators to halt the march of invasive species.
"It has been estimated that to manage Japanese knotweed in the UK, without successful biological control, would leave farmers, gardeners and local councils facing a bill of at least
Source: (bbc.co.uk)
By Navin Singh Khadka
Environment reporter, BBC News
An invasive plant is emerging as a major problem in a Nepalese national park renowned for protecting endangered wildlife species, say scientists.
The Chitwan National Park is listed as a Unesco world heritage site and is a major tourist attraction.
It has been a huge conservation success story, with nearly 100 breeding adult tigers and more than 400 rhinos roaming within its territory.
But a quiet intruder has emerged as a possible threat to the park's ecosystem.
"Already 50% of rhino's habitat is covered by this alien plant"
Naresh Subedi
National Trust for Nature Conservation
A native plant of Brazil, the weed Mikenia micrantha, has already covered 20% of the national park in southern Nepal.
Most of the affected areas are important to the tigers, rhinos and some endangered bird species - moist places and riversides that are conducive to the growth of the invasive creeper.
"Already 50% of the rhino's habitat is covered by this alien plant," says Naresh Subedi of Nepal's National Trust for Nature Conservation, which has carried out research in the Chitwan national park.
"If uncontrolled, it will spread over half of the park's entire area."
Suffocating creeper
Also known as "mile by a minute" because of its fast spreading rate, the weed can smother anything that gets in its way - from grasses to even large trees.
"As a result, we have seen some trees grow old quickly and die. And grasses [that many animals eat] have simply disappeared," says Narendra Man Babu Pradhan, chief warden of the park.
"We call this vegetation imposition."
Conservationists say that the impacts upon the park's animals.
"For example, there is this tree that bears fruits called 'rhino's apple' that is killed once it is covered by the [weed]. This means a food source for the rhinos becomes scarce," explains Mr Subedi.
Mr Pradhan says that different types of grasses, which form an essential part of the diets of small animals such as deer, are also disappearing from areas of the park invaded by the weed.
"The creeper alters the vegetation to such an extent that birds do not get the right natural setting for nesting and laying eggs"
Hem Sagar Baral, ornithologist
"Small animals need good quality food and these grasses are very important for them."
And if the deer are affected, this is likely to have a knock-on effect on the tigers' diet.
"There is a possibility that the food chain in the park is adversely affected," Mr Pradhan says.
Dr Richard Kock, a scientist with the Zoological Society of London (ZSL) says that the weed reduces "suitable cover" for the tiger. He is trying to help park officials to tackle the problem.
"It forces animals to forage more widely and outside of the park in farmland. This increases conflict and the risk of death from poaching or revenge attacks [by farmers whose crops are eaten up by park animals]," he says.
Spreading invasion
Park officials say they have seen some rhinos that have begun to eat Mikenia micrantha because they have "no choice".
"As megaherbivores, they need plenty of food, so we can imagine why some of them have begun to eat this plant," says Mr Pradhan.
And the droppings of these rhinos, and other herbivores that eat the plant, will spread the invasive weed.
The park officials have started to look into how Mikenia micrantha is affecting the rhinos.
They have attached radio collars to two rhinos and they will track six more in the same way in order to monitor their foraging behaviour.
They hope to have the results from this study within two years, but the invasive plant is likely to have spread far more by then.
It has already crept out of the park and is advancing towards the west. Latest findings show it has reached the Dang area in western Nepal.
Conservationists fear that, at this rate, it will soon reach the nearby Bardiya National Park - another protected area that has successfully conserved several endangered species, including tigers.
Out of control
Scientists say that the plant was first seen in the eastern part of Nepal, where it did some ecological damage to the Koshi Tappu wildlife reserve - a bird watcher's paradise.
"The weed covered areas near wetlands, grassland and open places in the forest. [It has caused a reduction in] the number of endangered swamp francolin birds in Koshi Tappu," says Hem Sagar Baral, a noted ornithologist in Nepal.
"The creeper alters the vegetation to such an extent that birds do not get the right natural setting for nesting and laying eggs.
"Species like the reed warbler and some thrushes are also declining there."
Although there is no clear record, conservationists say the plant probably came from India, where it was said to have been imported during World War II.
"It is believed that it was brought into India to camouflage army camps during the war," says Dr Baral.
Conservationists say that some national parks in the north-eastern part of India have also seen the spread of this invasive creeper.
Hands-on effort
Authorities have tried uprooting the plant from some sections of the Chitwan national park. Even Prime Minister Madhab Kumar Nepal rolled up his sleeves when he recently joined a "weeding" effort.
But this measure has so far proved unsuccessful because the plant has already covered wide areas. It continues to regrow, stimulated to spread by the movement of people and animals within the park.
Authorities do not want to use chemical or biological measures, which they fear could harm the park's ecosystem. So officials are left somewhat helpless.
Mikenia micrantha continues to grip this valuable natural site, stifling its vegetation and threatening its wildlife.
This article is from the BBC News website.