Category: habitats

‘Tis the season…or is it?

Posted on by andy.winfield

By Helen Roberts

As I sit at my desk this morning, staring out the window, the weather is dire. There is slanting torrential rain and high winds, a typical December day perhaps.
Here in the UK, the seasons are changing and we are experiencing extremes of weather. For example, we have had wetter, milder winters in the southwest over the last couple of years along with increased flooding, particularly on the Somerset Levels. And then there was the very slow start to spring this year, with temperatures well below average in April. This was followed by a very hot end to the summer and warmer-than-average temperatures throughout autumn.
These changes to the seasons are linked to global climate change and are throwing the UK’s wildlife into disorder and affecting the fine balance of habitats and ecosystems. This is not a good scenario for biodiversity in the UK. Seasonal timing is off. When seasons start and end is shifting, and the length of the season itself is changing, making ‘growing seasons’ a more fluid concept. There is also increased risk for most gardeners of a ‘false spring’. Many plants and animals are changing their geographical ranges in order to adapt to these changes.
One of the most significant effects has been the disruption of lifecycle events and these are manifesting themselves in different ways. Bird migration, insect emergence, incidence of pests and diseases and flowering times are being thrown out of kilter.  
Researchers from the University of East Anglia recently analysed 37 years worth of data from the UK Butterfly MonitoringScheme (UKBMS) and found that extreme weather events were causing population crashes of butterflies. Uncommonly high rainfall events during the cocoon life stage affected 25% of UK butterfly species. And more than half of species were affected by extreme-heat during the overwintering life stage, possibly due to the increased incidence of disease or the effect of a ‘false spring’, causing butterflies to emerge too early only to be decimated by a return to cooler temperatures.
Warm temperatures are not all bad for butterflies though, as they will benefit from hot temperatures over the summer months when they are in their adult form and resources are plentiful. However, if populations crash more frequently than they expand, these extreme weather events could threaten UK butterflies.
The spider orchid (Ophrys sphegodes).
Photo: Jacinta Iluch Valero via Flickr [Creative Commons]

Changes in seasonal timing are also knocking the relationships between plants and animals out of sync, including the delicate balance between plants and pollinators. Thiscan be detrimental to the balance of entire ecosystems. An elegant study carried out by scientists from Kew and the University of East Anglia found that earlier springs brought about by rising temperatures are affecting the relationship between a rare spider orchid (Ophrys sphegodes) and its sole pollinator, the solitary miner bee (Andrena nigroaenea).   

This particular orchid has a flower that resembles and smells like a female miner bee and it uses this deceit in order to lure the male miner bee in. The male attempts to mate with the flower and by doing so, pollinates the flower. The plant has evolved to flower at the same time as the male bees emerge, but before the females do.
What the researchers discovered, by looking at the data set going back to 1848, was that rising temperatures are causing the relationship between orchid and bee to break down. Although rising temperatures cause both the bee to emerge and the orchid to flower earlier, the effect on the bees is much more pronounced. The male bees emerge much earlier and the orchids now flower as the female bees emerge. This means the males are not “pseudocopulating” with the flower because the real thing is already available and so the rare spider orchid is having fewer pollinations.
However bleak this picture may seem, plants and animals do have the ability to adjust to seasonal changes caused by climate change, it is just whether they can adapt quickly enough for these intricate ecological relationships to remain intact.
Helen Roberts is a trained landscape architect with a background in plant sciences. She is a probationary member of the Garden Media Guild and a regular contributor to the University of Bristol Botanic Garden blog.


References

The resilient plants of the western Mediterranean

Posted on by andy.winfield

By Helen Roberts

A recent talk to the Friends by Dr Chris Thorogood on the flora of the western Mediterranean was tonic for those of us longing for warmer weather. For Chris, the western Mediterranean has always had great appeal having spent many summers teaching field courses to undergraduate students at the University of Bristol and the last five years conducting fieldwork for his new book, a field guide to the area.

“The flora of the Western Mediterranean is really special. The plants are able to grow in some fascinating but really harsh places,” explains Chris. “Because of these severe conditions, plants have evolved numerous coping mechanisms in order to survive.”

The region is extremely rich botanically, with over 10,000 different species, all of which are specially adapted to particularly taxing conditions. The area covers a huge geographical expanse incorporating the westerly Portuguese Algarve, to Italy in the east, the islands (Balearic Islands, Corsica and Sardinia) and North Africa from Morocco to Tunisia (see my post last week, which discusses these regions in more detail).

A bounty of habitats: scrubby landscapes

There is a diverse range of floral habitats in the region from the scrubby maquis to forests with wonderful understories of orchids. The bare and arid habitats are home to ‘experts’ in drought tolerance; and at the other end of the watery spectrum are the seasonal lakes where deadly predatory plants reside. Humans have shaped the flora as well through thousands of years of agriculture, which has produced a visually evocative landscape throughout the whole Mediterranean basin.

Cistus ladanifer, the common gum cistus.
Photo credit: Henry Bush [via Flickr, CC]

A habitat that we so often associate with the Mediterranean landscape is maquis, which is specific to the Mediterranean area. It is comprised of spiny sclerophyllous  (a fancy word for hard-leafed) tough vegetation, which is specially adapted to cope with severe drought. There are often small trees and shrubs dotted about, often with beautiful understories of bulbs and short-lived annuals. Many of the species are aromatic. Typical species include prickly juniper (Juniperus oxycedrus) and common gum cistus (Cistus ladanifer), both highly pungent plants that are used by the cosmetic industry for their oils.

“The smells that exude from maquis vegetation are wonderful,” exclaims Chris, “and the scent from these aromatic plants just seems to hang on your clothes long afterwards.”

Garrigue vegetation is similar to that of maquis. It differs slightly in that it is low growing in form, occurs closer to the coasts and grows on shallower soils. Due to its close proximity to the coast it is battered by winter storms and winds. The low stature of the garrigue evergreen scrub means that perennials and bulbs are highly visible. The flowering displays in spring are visually spectacular and include wild tulips, crocuses, thymes, mints, helichrysums and lavenders.

Into the woods

The native forests of the western Mediterranean form prominent landscapes occupying quite different terrain than the shrubland regions. The oak woodlands are dominated by the holm and cork oak, with a spectacular understory that offers a refuge for many animals, including the endangered Iberian lynx.

The pine forests of Pinus halepensis and Pinus pinaster occupy coasts and cliffs. Healthy habitats have a particularly distinctive flora and fauna with rarities such as the semi-parasitic Violet Limadore orchid found in the maritime pine forest of Landes in France.

Ceratonia siliqua, commonly known as the carob tree.
Photo credit: Jesus Cabrera [via Flickr, CC]  

Humans have also shaped the forest landscapes of the region to a certain degree. Traditional farming practices in the Mediterranean have created unique assemblages of plants. Olive, carob, fig and almond groves represent landscapes people often associate with the Mediterranean. No other landscape denotes the true essence of the Mediterranean like a grove of olives. The olive is engrained in the lives and culture of the people of the region. Carob groves are also stunning in their composition with the gnarly dark trunks contrasting brilliantly against the green understory. The carob, Ceratonia siliqua, is a member of the ‘peas’ (Fabaceae), the most speciose family in the Mediterranean.

Rare aquatic habitats

Most of the western Mediterranean habitats are dry and parched, but surprisingly there are some wet ecosystems too. These unusual habitats are rare and include some curious species like the carnivorous bladderworts, found in seasonal lakes, which catch insect prey using sticky hairs and trap doors.

“The aquatic habitats of the western Mediterranean are interesting because they are pretty rare,” explained Chris. “Many are only seasonal but they support a wealth of interesting species from tiny forget-me-nots, tongue orchids and the carnivorous bladderworts.”

Tough but not invincible

While the native species of the western Mediterranean might be seen as tough and indestructible in the harsh landscapes they occupy, they are extremely susceptible to invasive alien species (IAS). Chris explained that the two most invasive plants in the region include certain species of Eucalyptus and Acacia. People assume these species are native, probably because they fit into the landscape visually and they can tolerate harsh climatic conditions. However, both these trees can alter native ecosystems and have a negative impact on biodiversity. Unfortunately, many are still planted as ornamental shrubs despite measures drawn up to prohibit the cultivation of them.

Chris explains the danger of one such exotic: “Acacia cyclops is an invasive species that is likely to become the next big invasive in the western Mediterranean. This species forms a mass of vegetation in barren landscapes due to its ability to cope with extremely dry and saline conditions. Ultimately it outcompetes native species.”

These invasive pests steal native plants’ water and change the biochemistry and microbiology of the soil. The native flora is sensitive because the western Mediterranean is exceptionally biodiverse in a relatively small area, with high levels of endemism, particularly on some of the islands. As well as the threat from IAS, there is also intense pressures on these fragile native habitats from humans due to urbanisation, afforestation, and coastal and agricultural development. Effective and timely conservation measures are vital to ensure the survival of these beautiful and botanically rich habitats before it is too late and they go into decline.

Helen Roberts is a trained landscape architect with a background in plant sciences. She is a probationary member of the Garden Media Guild and a regular contributor to the University of Bristol Botanic Garden blog.

Floral visits to the western Mediterranean

Posted on by andy.winfield

By Helen Roberts

A floral excursion to the western Mediterranean at this time of year appeals to many of us. The anticipation of warm weather, beautiful landscapes and a dizzyingly diverse range of exquisite wild flowers and I want to pack my bags in a flash. I certainly felt that way when I saw some of the images of the region’s wild flowers in a recent Friends‘ talk given by botanist Dr Chris Thorogood.
However, if you cannot escape overseas, then the Mediterranean collection at the University of Bristol Botanic Garden will give you a taste of some of the Mediterranean Basin species although you will have to wait till later in the year to see some of the flowers in bloom. 
If you do have a trip in mind though, here are a few of Chris Thorogood’s favourite spots to see the wild flowers of the western Mediterranean:
Cape St Vincent, Portugal. Photo courtesy of Peter Broster via
Flickr [CC license]

The Algarve, Portugal:

This area has a diverse flora due to varied geology and weather with numerous endemic species and beautiful wild flower meadows. Cape St Vincent, the most south-westerly point in the area and a vast nature reserve, has a spectacular display of flowers in the spring and early summer (January through to the end of May). There are many unique species of thyme and endemic rarities like the tiny diamond flower (Ionopsidium acaule).

Almeria, Spain:

This province is located in the southeast of the Iberian Peninsula and has a wealth of species adapted to cope with extremely dry conditions. Many plants are salt tolerant including sea lavenders like Limoniuminsigne and the rare low growing lily, Androcymbium europaeum whose flowers emerge on sand dunes in mid winter. An area called Cabo de Gata, an impressive tract of volcanic cliffs, is host to numerous unusual species. Many of these are freakishly odd looking from the succulent Caralluma europaea with its purple and yellow striped flowers to the phallic form of the parasitic Cynomorium coccineum.

Cap de Formentor, Mallorca:

This peninsula in the northeast of the island has many unique sea lavenders and orchids. Endemics are closely dotted only metres apart. Much of the landscape is fairly inaccessible due to its rocky and precipitous nature so one needs to be fairly adventurous to spot some species. Notable endemic species include Arum pictum, an arum that smells of rotten meat to attract its fly pollinators and a species of St John’s Wort unique to Mallorca, Hypericum balearicum.

Maremma, Southern Tuscany, Italy:

The Maremma region is rich in wild flowers and contains 25% of all Italian flora. It has a unique geology and extremely varied landscapes including the protected coast, swathes of pine forest and abandoned agricultural plains. The giant fennel, Ferula communis, is one such distinctive plant with its towering inflorescences that can take many years to develop.

Gargano National Park, Puglia, Italy:

The yellow bee orchid (Ophrys lutea) is one of the orchid
species found in Gargano National Park.
Photo credit: Alastair Rae [via Flickr, CC license]
This park has a unique flora and are highly specialised for growing in certain conditions many being endemic. The park covers a vast area and as a result the landscapes are varied from rich beech forests, steep cliffs, karstic plateaus and scrubby maquis. There are many orchid species here (over 65) including some unique bee orchids.

Helen Roberts is a trained landscape architect with a background in plant sciences. She is a probationary member of the Garden Media Guild and a regular contributor to the University of Bristol Botanic Garden blog.