Environmental experts have underlined the need to increase conservation efforts as more than a third of the world's trees face threats of extinction.
A report issued this week by the International Union for Conservation of Nature found that 38 per cent of trees are at risk due to factors such as deforestation and the loss of land to agriculture, with stark consequences for biodiversity and people.
A wide range of measures are being taken to preserve and propagate tree species, including the collection of seeds for long-term storage.
One scientist involved in the assessment, Dr Steven Bachman, a conservation assessment and analysis researcher at the Royal Botanic Gardens Kew in Britain, listed Kew’s Millennium Seed Bank as an example of measures that could save species. The bank is an underground collection of 2.4 billion seeds in Sussex in south-east England.
“Also, botanic gardens around the world, linked through Botanic Gardens Conservation International (BGCI) can propagate and grow trees for their living collections as a form of ‘ex situ’ conservation,” Dr Bachman said.
Targeted planting programmes
Emily Beech, head of conservation prioritisation at the BGCI, which links botanic gardens in more than 100 countries, said it is important that native trees, especially threatened species, were planted to help restore populations.
A project involving BGCI focuses on a magnolia tree in China called Magnolia omeiensis, which has been threatened by logging to such a degree that only about 75 trees remain in the wild.
The species, found only in two locations in China’s Sichuan province, is particularly at risk because of its low seed yield and germination rates.
A centre called the Sichuan Provincial Institute of Natural Resource Sciences, along with Chinese partners, has been growing a stock of the species so they can be planted in the wild.
Studies are taking place to enhance propagation techniques, with one aim being for local communities to propagate the species in their gardens.
Assessing the root cause
Previous research by Kew and the BGCI has indicated that planting the wrong types of trees can cause more harm than good to nature and people. Careful monitoring is needed, experts say, to ensure that projects offer the greatest benefits.
The significance that trees have for people is illustrated by the fact that more than 5,000 tree species are used for timber in construction, while more than 2,000 species have medicinal properties, Ms Beech said.
More than 2,000 tree species are used as fuel, with many communities continuing to rely on fuel obtained from forests.
“Increasingly we are also recognising that trees and woodlands are so important for our own mental well-being by providing places of calm and reflection and a connection to nature that is so important in our busy lives today,” Dr Bachman said.
As well as being of great value to people, trees are also important for other forms of life, including mammals, birds, reptiles, amphibians, insects, other plants and fungi.
“They provide an important resource for these other species, as well as regulating the carbon, water and nutrient cycles. People have been citing tree planting as a way of combating climate change to increase carbon storage,” Ms Beech said. “There are lots of tropical forests with many species in a small area. When we lose that, we lose huge amounts of diversity. The knock-on effect for all these ecosystems is huge.”
Numbers of threatened species are higher in the tropics, reflecting at least in part that there are more tree species in tropical areas.
However, this week's findings indicate that trees in 192 countries are threatened with extinction. Dr Jean-Christophe Vié, director of the Fondation Franklinia, a Swiss-based organisation that provides grants to support tree conservation, emphasised that threats to trees are global, even if some studies have indicated that tree cover in some temperate regions, such as parts of Europe, has increased.
“Sometimes it's just monoculture, things that have been planted. It's like a field of corn; it's not properly forest,” said Dr Vié, who is a member of the advisory board of the Mohamed bin Zayed Species Conservation Fund. Such monocultures do not support a wide variety of other organisms in the way natural forests do, he added.
“If they were proper forests, forest birds would do better,” Dr Vié said. “There are very few, in Europe, pristine forests. Proper forests are being reduced at an alarming rate, including in Europe. We need to change completely the mindset of the forestry sector. Stop these monocultures and spraying of insecticides, give more space to nature to do its job.”
Dr Vié said there should be tighter controls globally on the timber sector, including greater efforts to stop “the massive illegal timber trade”.
Disease and deforestation
The IUCN said that island tree species were particularly at risk, with invasive species, pests, diseases and deforestation often cited as contributing factors.
The IUCN said this week that its Red List, which describes the conservation status of plants, animals and fungi, includes 47,282 tree species, of which 16,425, or 38 per cent of trees on the Red List are threatened.
The Red List includes 166,061 species in total, of which 46,337 are threatened. There are more than twice as many threatened trees as there are threatened birds, mammals, amphibians and reptiles combined.
Dr Bachman said that trees could be effectively conserved, although “ongoing monitoring is needed as threats may increase in the future”.
As an example of a success story, he cited a variety of pine trees with the scientific name Pinus caribaea var. bahamensis found in the Turks and Caicos Islands in the Caribbean.
After it was discovered that this tree was threatened by an invasive non-native and pine-specific tortoise scale insect, a recovery programme was established.
“This involved prescribed fires to promote forest growth, propagation of pines in living collections and the reintroduction of more than 450 seedlings that showed a high – over 80 per cent – survival rate,” he said.
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