A fifth of the world’s plants under threat, as report says 391,000 species now known to science

Dave Simpson – 11 May 2016

A ground-breaking report from the Royal Botanic Gardens, Kew, has produced an estimate of the number of plants known to science. By searching through existing databases, the researchers have estimated that there are now 390,900 known plant species, of which around 369,400 are flowering plants. But this figure is only those species currently documented: new species are being discovered all the time, including over 2000 in 2015 alone. But more worryingly, it is suggested that 21% of plant species are under threat, from a range of pressures including climate change, habitat loss and invasive species. The invasive species component of the report, which draws heavily on CABI’s Invasive Species Compendium, says that nearly 5,000 plant species are documented as invasive, from over 13,000 vascular plant species naturalised outside their native range.

Prof Kathy Willis, director of science at RBG Kew, said: “It’s really important to know how many plant species there are, where they are and the relationship between the groups, because plants are absolutely fundamental to our well-being”

And on invasive species, the head of conservation science at Kew, Dr Colin Clubbe, said that invasive species are one of the biggest challenges for biodiversity. Quantifying the number of species regarded as invasive is a key step towards addressing the problem. “Now that we’ve got this list and this number, it’s certainly a bit like know your enemy,” said Dr Clubbe.

JK

Japanese knotweed, a major invasive
“We know what we are dealing with, we can then look at them, and see what’s similar, what makes a good invasive, and then see how we can use that information to have better management practices in place or recommendations for how you deal with them.”

 
Trade, plant collecting, and movement of people, has led to at least 13,168 species of vascular plants becoming naturalised outside their native range. The report says that they become classed as invasives once they start to compete with native vegetation and spread to a degree that causes damage to the environment, the human economy or human health. The effects on livelihoods, and on ecosystem services such as agriculture, forestry, water and pollinators, can be staggering: the Kew report cites one study as estimating the total costs from all invasive species as nearly 5% of the world economy, and it also quotes CABI research which estimated the impact on the British economy alone as around £1.7 billion every year. Japanese knotweed, one of the most invasive plants in the UK, costs Great Britain over £165 million annually to control.

The Kew report synthesizes invasive species data from the open-access CABI Invasive Species Compendium, the Global Invasive Species Database (GISD), global reviews of invasive trees and shrubs by Rejmánek and Richardson, and Weber’s Invasive Plant Species of the World: a Reference Guide to Environmental Weeds published by CABI in 2003. CABI’s ISC – flagged in the report as “the most comprehensive web-based resource” – has datasheets for 4,841 of the total of 4979 invasive vascular plants in Kew’s consolidated list.

Identifying other threats to plant biodiversity, the report says that farming is the biggest extinction threat, representing 31% of total risk to plants. Logging and the gathering of plants from the wild is responsible for 21.3% of the risk, followed by construction work with 12.8%. The report said that some 1,771 areas of the world have been identified as “important plant areas” but very few have conservation protection measures in place.

Highlighting just how many plant species are already important to humans, the report says that some 17,810 plant species have a medical use, 5,538 are eaten, 3,649 become animal feed and 1,621 are used for fuels. Over 11,000 plant species are used for materials, for example fibres and timber.

“[Plants] provide us with our food, our fuel, our medicines – even controlling our climate” says Professor Willis.

The report can be downloaded in full, or data from individual sections accessed, at the website stateoftheworldplants.com. A symposium on the report is being held at Kew on 11-12 May. Moving forward, the global assessment will now be carried out annually, allowing scientists to monitor how plants are changing over time.

New Strategy Receives Thumbs Up

Group photo GA 2015

This week in Douala, Cameroon, the General Assembly of the African Union’s InterAfrican Phytosanitary Council (IAPSC) gave the thumbs up to IAPSC’s new strategic plan. IAPSC Director Dr Jean Gerard Mezui M’Ella thanked all the organisation’s partners who had assisted in the preparation of the plan, especially FAO’s Regional Office for Africa for funding the work. Titled “For Better Plant Health in Africa”, the plan identifies four key impact areas, and names a number of partners, including CABI, whose support will be important in its operationalization.

Following on from earlier discussions with IAPSC, CABI Africa’s Roger Day made a presentation on “A Plant Health Management System (PHIS) for IASPC”, corresponding to output 2.3 of the strategy. The ideas were well received by the General Assembly, which immediately appointed a small task force to develop a proposal as a basis for mobilising resources. The General Assembly also adopted a resolution saying it “Welcomes the cooperation between CABI and IASPC on Plant Health Information Systems, and urges them to develop further the ideas for putting in place an effective PHIS, and calls upon international partners to avail financial and technical resources for implementing such an important project”.

For further information contact IAPSC (au-cpi@au-appo.org) or CABI (Africa@cabi.org).

Tackling Tutsan

Tutsan (Hypericum androsaemum) is invasive to New Zealand and Australia. Native to many countries throughout Europe and western parts of Asia, it is thought to have been introduced as a garden ornamental by acclimatisation societies in the 1800s due to its attractive yellow flower. Today, tutsan is a severe weed in several regions of New Zealand, most significantly affecting the Ruapehu District and Bay of Plenty region in the North Island. Over the last 20 years, tutsan has become an increasing problem in these regions; spreading throughout low fertility pastures and along roadsides. There is concern that tutsan has the potential to pose a significant conservation threat if it continues to spread at its current rate through scrub and native forest fringes.

Flowering tutsan plants growing in New Zealand (photo: Lizzie Rendell, 2011)

Flowering tutsan plants growing in New Zealand (photo: Lizzie Rendell, 2011)

Recent estimates indicate that around 150,000 ha of land in the Ruapehu district is affected by tutsan. Within the district, the annual cost of controlling the weed, and loss of farming profit amount to around $NZ1.2 million (£600,000), and loss of current land values is estimated at $NZ27 million (£13 million). Tutsan is a persistent weed for which there are no registered chemicals. Off-label herbicides are currently used in an attempt to limit its spread, but these are proving ineffective with stands typically reappearing several years later. The weed is unpalatable to stock and the topography of the region’s worst affected areas further limits the control methods possible. Read more of this post

Invasive myrtle rust impacts discussed at international forestry congress

CABI has recently published a comprehensive review and update of its ISC datasheet on the globally important pathogen Puccinia psidii, commonly known as myrtle rust or guava rust. This problematic fungus is of worldwide importance and is capable of infecting a wide range of hosts. To date it has over 440 host species; affecting many plants in the Myrtaceae family, including threatened and endangered species (see IUCN Red List of Threatened Species). Severe impacts have been recorded in amenity plantings, commercial plantations and the native environment.

Once established in a new country myrtle rust can spread quickly and this has been the case in many countries including Jamaica, Hawaii, Australia and New Caledonia. Its successful global and local dispersal through urediniospores and human-aided movement of diseased plants, combined with its massive host range make myrtle rust an effective and devastating invasive. It was first identified as an invasive pathogen in the 1930s when it caused extensive damage to allspice (Pimenta dioica) plantations in Jamaica.

Puccinia psidii on Melaleuca quinquenervia in Australia

Effects of the invasive myrtle rust (Puccinia psidii) on the paperbark tree (Melaleuca quinquenervia) in Australia (July, 2011)

Discussions of myrtle rust impacts and a variety of other forestry related issues are currently underway at the 24th IUFRO World Congress, which is being held from the 5th-11th October 2014 in Salt Lake City, USA.

IUFRO is the International Union of Forest Research Organizations – the world’s forest network. The organisation promotes global cooperation on forest-related research and is composed of over 15,000 scientists from 650 member organizations in more than 100 countries.

The Congress is the largest forest research conference worldwide and is held every 5 years. It brings together delegates from varying forestry backgrounds and this year over 3500 scientists, researchers, graduates, decision makers, policy makers and land managers are expected to attend the event, which is focused on “Sustaining Forests, Sustaining People: the Role of Research”. Over the course of the week a number of plenary, sub-plenary, technical and poster sessions will cover themes, such as:

Under the theme of Forest Health in a Changing World, a session dedicated to emerging invasive forest pathogens will see notable speakers discuss the impacts of myrtle rust in the southern hemisphere, including its effects on diversity in both Australia and Hawaii (see p103-104 of the Scientific Program). This session will also focus on ash dieback and the invasive pathogen Hymenoscyphus pseudoalbidus, which causes the disease in ash trees. This pathogen has recently been causing severe impacts across Europe.

For full details of the distributions, impacts, descriptions (and much more!) of both ash dieback and myrtle rust you can access the fully updated and peer reviewed datasheets on CABI’s open access Invasive Species Compendium.

To keep up to date with all the latest news from the 24th IUFRO World Congress, visit the blog here.

Getting swamped: Australian swamp stonecrop (Crassula helmsii) in the UK

In January this year, large parts of southern Australia were ablaze with fierce bush fires, while most of the UK was covered in snow. Half a world away from each other, and at one point nearly 40ºC apart, there aren’t too many similarities to be drawn between the two locations. And yet, there is a water weed, Crassula helmsii, that survives happily in both extremes – and in the UK, where it has been introduced, this adaptability is proving extremely problematic.

 Crassula helmsii, also known as Australian swamp stonecrop or New Zealand pygmyweed, is a small semi-aquatic plant in the Crassulaceae family. As its common name implies, this low-growing succulent originates from the antipodes, but was introduced to Britain from Tasmania almost 100 years ago. Initially sold by garden and aquatic centres as an oxygenating plant, by the 1950s it had established in the wild, and from there it has spread to numerous ponds, lakes and waterways throughout the UK.

A mat of Crassula helmsii in flower

A mat of Crassula helmsii in flower

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Rhododendron ponticum – much more than just an invasive weed!

Rhododendron ponticum, native to southern Europe and south west Asia was introduced into the UK in the 18th Century. Since then, this plant has grown uncontrollably and is now a common sight throughout western parts of the British Isles in areas such as Cornwall, Wales and parts of Scotland and Ireland. Despite producing an attractive flower in the spring, Rhododendron can have damaging effects on the local environment. By growing rapidly this plant outcompetes native flora, decreases biodiversity and furthermore constitutes a sporulating host for the two devastating pathogens Phytophthora ramorum and Phytophthora kernoviae, meaning these pathogens not only infect but also reproduce on R. ponticum.

Rhododenron ponticum

A stand of invasive Rhododendron ponticum in Windsor Great Park (Picture copyright CABI).

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Biological control of Mikania micrantha: Have we found the silver bullet?

Mikania micrantha (mile-a-minute weed or South American Climber) is a major invasive alien weed in many of the tropical moist forest regions of Asia.  This neotropical vine is able to smother plants in agricultural ecosystems, agroforestry and native habitats.  Conventional control methods of manual removal (slashing) or herbicide application, are expensive, ineffective, not sustainable, and can be environmentally damaging.  Classical biological control was considered the best option to manage this weed, and CABI was funded by DIFID (UK- Department for International Development) to implement this strategy in India.  The research culminated in the release of a coevolved, host specific, rust pathogen (Puccinia spegazzinii), from the South America native range of the weed, into Kerala and Assam.  This rust pathogen infects all aerial parts of the plant (leaf, petiole and stem), leading to cankering and whole plant death (see image below).

Puccinia spegazzinii Nov 10

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