Tag: Invasive Species

Dipping a Toe into the Natural History of Crete

A week ago, I begrudgingly returned home from a spur of the moment family holiday in Crete – a part of Europe I had yet to visit which, in retrospect, turned out to be rather beautiful. The week was marked by blissful temperatures, great food, a lively local culture and numerous excursions on foot to investigate the natural history of the rugged, olive-riddled land around Elounda.

As ever, birds formed the basis of most of my forays. The undisputed highlight of my time here comes from the countless Griffon Vultures noted high above the crags to the rear of our apartment. An undeniably awe-inspiring species which I will never tire of, joined on occasion by the odd Buzzard, Kestrel and, as the week drew to a close, a Golden Eagle lazily riding the thermals thrust upwards from the crumbling limestone escarpment. I am led to believe that Golden Eagles are not all that abundant on the island, thus I am quite happy with this one.

Elsewhere, multiple trips into the tightly-packed olive growths carpeting the land around Elounda provided some welcome sightings. A small flock of European Beeater, kaleidoscopic in the midday sun; a pair of Red-backed Shrike, multiple Blue Rock Thrush and a healthy number of both Crested Lark and Sardinian Warbler. Species one would struggle to encounter in the UK. Although, that said, more familiar species were abundant also: the gnarled old trees, rife with succulent purple fruits, teeming with Spotted Flycatcher, Willow Warbler, Great Tit, Goldfinch and House Sparrow – at least some of which turned out the be Italian Sparrow. The persistent kronking of Ravens overhead, a welcome soundtrack to the week’s sweaty wanders.

A further highlight came from the swirling mixed flocks of hirundines and swifts noted early each day in the skies above the resort. Familiar species, House Martin and Barn Swallow, mixed with the less familiar shapes of Crag Martin and Red-rumped Swallow. As for the swifts, it was lovely to finally gain good views of Alpine and Pallid Swift.

Scrutinising the botanical community of the local area, it was interesting (if a little troubling) to note the sheer abundance of invasive species present within what was a relatively small corner of the island.  Prickly Pear, Opuntia ficus-indica, and fearsome looking Eve’s-pin Cactus, Austrocylindropuntia subulata, added an element of peril to walks in rocky areas; whilst sprawling drifts of Hottentot Fig, Carpobrotus edulis, carpeted the ground in more shaded locations. Add to these no end of Century Plant, Agave americana, naturalised Hibiscus and Aloe Vera and the problems facing this Mediterranean Island become quite clear. The sheer domination of invasive species here is further emphasised by the presence in a wild setting of three species familiar from my own living room: Jade, Crassula ovata, Mother of Thousands, Bryophyllum daigremontianum, and African Milk Tree, Euphorbia trigona.

I should note that I did also find time to enjoy some native botanicals, albeit those that had not yet withered beyond recognition due to lack of rainfall. A personal favourite coming from the curious looking Exploding Cucumber, Ecballium elaterium.

Exploding Cucumber (Ecballium elaterium)

Moving on to the insect life present in close proximity to our temporary abode and as far as butterflies go, pickings were surprisingly slim. The most abundant species being Painted Lady, closely followed by the stunning Swallowtail. The smaller blues, warmed and energised by the persistent sun, were far too quick to identify, unfortunately. Although, multiple run-ins with Hummingbird Hawk-moth more than made up for this. As did my first encounter with the Cretan Cicada, Cicada cretensis.

Generally speaking, insects were few and far between on Crete. By far the most prevalent, at least in terms of biomass, were the hornets which, despite spreading fear among the ranks of the countless tourists beached around the pool, proved far from intimidating. Initially, I had assumed these were European Hornet; although upon closer inspection, they turned out to be Oriental Hornet, Vespa orientalis. A new species for me and one whose European distribution is limited only to Greece and other nations in the Southeast.

The abundance of hornets in the area was matched only by that of the aptly named Black-and-Red-bug, Lygaeus equestris. A species which managed to find its way everywhere: from inside our room, to inside my glass of Ouzo on more than one occasion. Numbers, however, are not everything and an honourable mention goes to the large, impressive and extremely vivid Socalid Wasp pictured below. I confess that I have not been able to identify this species. Any thoughts?

These are only a few observations from what was a holiday intended not as a ‘nature expedition’ but as an opportunity to relax and catch up with family. As I am sure readers of this blog will testify, however, it is difficult not to at least try to observe wildlife when travelling abroad. I, for one, am quite satisfied with the variety of life unearthed in the vicinity of Elounda, particularly given my inability to travel further afield, and would very much like to revisit the island in the future. This time, with the express intent of observing and enjoying the more iconic species that call Crete home.

An hour in the company of aliens

Britain’s cities have served as the epicentre for countless invasions over the years. Landing sites, if you would, where species from far-flung destinations – East Asia, North America and closer to home, in Europe – gain first a toe-hold before beginning their creeping advance across the land. Here, in the city, the wheels of countless vehicles transport seeds, tenacious pioneers breach the walls of their manicured garden cells and unwitting homeowners provide an endless supply of food, sustaining some feral beings on their quest towards colonisation.

Yesterday, I decided to pause and look. To take a moment to seek out the non-native species with whom I share my street  (a small area of no more than 300m). I must confess, I was quite surprised – many, it seems, find the urban realm much to their liking.

Rising triumphantly between the pavement slabs that line the street adjacent to the fractured glass of the bus stop from which I make my daily commutes, the obnoxious yellow blooms of the day’s first invader add an unseasonal touch of colour at a time when little if anything, should flower. Oxford Ragwort, a native to the lava fields of Sicily, so named for the botanical gardens where the plant was first grown in the 1700s, clearly at home in the cracks and crevices provided by splitting concrete and crumbling wall.

Oxford Ragwort and Red Valerian growing side by side

So prolific is the ragwort here that it is easily the most frequently encountered ‘wildflower’ on the street, rivalled only by the less widespread yet thriving swaths of Red Valerian – another Mediterranean immigrant – which likewise finds the degrading stonework here to its liking. Both do well here, despite an annual dose of herbicide courtesy of the local council.

The invading botanicals here appear to have organised themselves quite well into some semblance of a natural, tiered community. While ragwort and valerian dominate at ground level, Buddleia prevails at altitude: standing tall in neglected gardens, atop walls, on rooftops and even chimney stacks. The dominant species in the sparse canopy of the street which, brick-breaking tendencies aside, I actually find myself gazing upon fondly. This invader, perhaps more so than the others, provides a boon to insects [and those who enjoy them] throughout the summer months.

While I see Buddleia everywhere I look on my street, some new arrivals are just beginning to gain a toehold. Along the railway lines some 25m from my front door, patches of much-maligned Japanese Knotweed have now appeared. In cracks and crannies on the sunnier side of the street, Trailing Bellflower – a native to the Alps – has begun to creep gradually from garden to garden. Each plant set to paint the stonework here a pleasant blue later in the year. There are others too: a passing glance at the exposed soil at the base of nearby lampost revealing a small, nondescript holly-shaped plant. Not our native Holly at all, in fact, but Oregon Grape – a spiny import from Western North America where, in its natural environment, it forms a dense understory in the shade of towering Douglas Firs. It will find no fir trees here – not that it will be deterred.

Heading to the local park, keen to seek out something, anything, which truly belongs, a piercing shriek and a series of gleeful whistles herald the arrival of another uninvited guest. Sure enough, moments later, a lurid green parakeet emerges atop a budding sycamore. A bird hailing from East Asia, perched in a tree of Eastern European origin looking out across a street laden with arrivals of North America, Italy and China… all in one tiny corner of Britain.

Say what you will about invasive species, they do, in my opinion, deserve some degree of respect for carving out a home in what are often entirely unnatural settings. Some are damaging, some are relatively harmless, but all are interesting.

The exotic heart of London

Hailing from the North East of England, to me, a visit to London is much like a visit to a dystopian future. One where geographical boundaries blur and species which naturally should never have encountered one another, stand cheek by jowl in an odd assemblage of the tropical and tenacious. From squirrels, birds and fish to the very trees that make up the backbone of the city’s parks, wildlife watching in London is a queer old affair.

Killing some time between professional commitments upon a recent trip ‘down south’, it would have been rude of me not to visit at least a few of London’s many sprawling parks. And I did: calling first at St. James’s to enjoy its otherworldly assortment of wildfowl – both captive and wild. Admiring the numerous Egyptian geese, hamstringing passers-by for a free meal in the company of feral Bar-headed Geese – originally from Asia – and the odd free-flying Black Swan. Whether or not the latter were part of the parks extensive collection remains open to speculation. Coupled with the odd Mandarin, these helped set an altogether tropical tone to our stay in the capital.

Egyptian Geese

The collections at St. James’s were interesting too, of course. Paramount to any zoo and providing a great opportunity to brush up on my exotic waterfowl ID – with Ruddy Shelduck, Hooded Merganser, Red-breasted Goose, Fulvous Whistling Duck and Ross’s Goose present to name but a few. Not to mention the world-famous Pelicans doing their utmost to delight the amassed crowds. I confess, I was quite taken by them.

Famous pelicans, with bonus Ruddy Shelduck and Red-breasted Geese

Departing St. James’s, we headed for Hyde Park – brandishing an apple so to [hopefully] gain a closer look at one of the capitals most prolific alien residents: Ring-necked Parakeets. We were not disappointed, and after almost an hour of hearing the characteristic, piercing shrieks of this species from high in the canopy of London Plane – another non-native species – soon found ourselves covered head-to-toe in lurid green birds. The characterful parrots just as confiding as the countless pictures posted to social media had suggested: adorning head and arm alike as they squabbled for prime, fruit-stealing position. With some even going so far as to deliver a short, sharp bite when not immediately pandered to – impatient Southerners.

Up-close and personal with London’s parakeets

While some find themselves conflicted regarding Grey Squirrels [we saw an ungodly amount of these in London too] I, like many others, find myself torn on Ring-necked Parakeets. On one hand, they are potentially damaging invasives: killing bats, extirpating native birds from nest holes and plundering food crops. They are noisy, brazen, disruptive and at the base of things, should not be here. On the other hand, they are rather beautiful, and for many in the city, provide a much-needed link to the natural world. One they are familiar with. Honestly, I could not help but feel charmed by the birds and, with their permanent status in Britain all but assured, see no harm in celebrating them for what they are: adaptive and resilient colonists. Much like ourselves.

Parakeets, waterfowl and invasive squirrels aside, I would like to say that I also noted an abundance of native species in London. I didn’t. By large, most of the species seen and enjoyed were colonists – each impressive in their own way. Something which, if little else, serves to help me understand the difficulties faced when we conservationists openly and fiercely discuss the need to control, limit and destroy non-native species. For some, species such as this – the parakeets, grey squirrels and Egyptian Geese of this world – are all the wildlife they know. Little wonder then that some choose to defend them so vigorously. I might not agree, but I do understand.

 

Top 10 Facts: Surprising UK Non-Natives

American Bullfrog Lithobates catesbeianus. Around twice the length of our native Common Frog, American Bullfrogs are most often identified by their loud, deep calls. Deemed a risk to British wildlife due to their tendency to prey on everything from small mammals and ducklings to other amphibians, Bullfrogs may also spread Batrachochytrium dendrobatidis – a form of Chytrid fungus – to native amphibians. Due to their negative impact on the native ecosystems, bullfrogs have been subject to an eradication scheme, costing up to £100,000 to date. Despite conservationist’s best efforts, this species remains present in a select few areas across England. Did you know that bullfrog tadpoles can grow up to 15cm?

Topmouth Gudgeon Pseudorasbora parva. Widespread but scattered across England, Topmouth Gudgeon inhabit well-vegetated ponds, channels and lakes. This nondescript fish species compete with native fish and farmed stock for food, and has been found to severely deplete or even eradicate native fish and invertebrate populations in areas of particularly high density – gudgeon have been recorded at densities of up to 60 fish per square meter – and has been directly linked to the eutrophication of British waterbodies due to it’s feeding tendencies which limit zooplankton abundance. Thus, in turn, increasing phytoplankton prevalence.

Coati Nasua nasua. A close relative of the North American Raccoon, up to ten animals were known to be living wild in South Cumbria until at least 2008. Given the small-scale of the reported population there are no known environmental impacts at present; though it is thought that, should this population expand or future escapes occur, that the Coati could become a significant predator of native wildlife. South Lakes Wild Animal Park was initially implicated in the spread of Coati’s in Cumbria, although the spread of sightings – ranging from Kendal and Kentmere to Langdale and Penrith – suggest other possible escapes.

American Skunk-cabbage Lysichiton americanus. A rather conspicuous plant boasting yellow flowers aesthetically similar to native Lords and Ladies, the stronghold of Skunk-cabbage appears to be Southeast England, most notably Hampshire. Although populations now exist at various intervals between Cornwall and Inverness. Like many invasive botanicals, this species is thought to decrease floral diversity within occupied areas and it is thought – based on Germans studies – that it can have a significant impact upon marshland plant communities. The economic impact of American Skunk-cabbage remains unknown; though with the species seemingly consolidating its hold in the UK, it is likely that further study will be needed to properly assess its impact.

American Skunk-cabbage

Quagga Mussel Dreissena bugensis. In October 2014 Quagga Mussel was found in Wraysbury Reservoir and the Wraysbury River, near Egham, Surrey –  the first UK record of this decorative yet damaging species. Originally from the Ponto-Caspian region, the mussel can significantly alter whole ecosystems by filtering out large quantities of nutrients and is also a thought to pose a serious biofouling risk by blocking pipes and smothering boat hulls. It is thought that there are no effective eradication techniques for Quagga Mussel once it becomes established, thus all records of this species should be reported immediately.

Carolina Wood Duck Aix sponsa. The wood duck is the only congener of mandarin duck and females and young birds are hard to distinguish from that species – meaning that this species may go unrecorded in many instances. First reported in the wild during the 1830’s Wood Ducks have been recorded breeding at many locations across the UK including in Wiltshire, Berkshire, Devon and Kent. Despite this, the species has not yet formed a self-sustaining population anywhere in the UK. While there is potential for Wood Ducks to compete for nest-sites with other hole-nesting bird species, this is one non-native species that does not appear to have an overwhelmingly negative impact on the British ecosystem. With escapes from captivity still relatively common, it is likely that individuals will continue to be found wild long into the future.

Carolina Wood Duck

Pitcher Plant. There are currently twelve known populations of this carnivorous plant species known from the UK, with the largest being found on Wedholme Flow where there are ongoing efforts to control numbers. The species has been eradicated from a further ten sites across the UK; where the vector for introduction was thought to be transplanting from private collections. Large Pitcher Plant populations have been shown to restrict the growth of native botanicals and, based on studies in Ireland, it is thought that the species may impact upon peat regeneration due to its tendency to restrict the growth of Sphagnum Moss. There are no known economic effects of this species, with the cost of removal covered, to date, by conservation bodies in charge of the reserves on which it grows.

Wels Catfish Silurus glanis. Growing up to 3m in length across its native range in Europe and Asia, this catfish is a voracious predator of birds, mammals, amphibians and invertebrates and. as such, there is concern that the presence of this species within UK waters may have an adverse effect on biodiversity. Indeed, studies from Spain suggest that the Wels may have a detrimental impact on waterbird populations. Widespread but scarce in the UK, the majority of Wels sightings come from Southern England where, despite expert advise, it is continuously stocked for sporting purposes. The first official record of this species living wild in the UK was at Morton Hall, Norfolk during 1864.

Wels Catfish

Tree-Of-Heaven Ailanthus altissima. With elongated, pinnate leaves, this species appears not dissimilar to Walnut or Ash and is planted heavily in urban areas. This has led to its escape in Southern England – occurring to such an extent that it has now become invasive in the London area. The impact of Tree-Of-Heaven remains relatively small due to its presence in areas of low conservation value; though it is thought that as temperatures warm, the species will acclimatise more readily to the natural ecosystem. In areas of Southern Europe – where the species has already established – Tree-Of-Heaven has been shown to actively exclude native flora. The plant also poses a slight risk to humans with the mild toxins found within the leaves often causing dermatitis upon contact.

Killer Algae Caulerpa taxifolia. A bright green seaweed with upright leafy fronds, dense growths of this marine plant can significantly alter habitat structure by displacing both floral and faunal species. It is also inedible to most native species, has been shown to smother sea-grass meadows – an important habitat type for many native marine species – and causes myriad problems for humans by reducing fish stocks and impacting upon the performance of fishing gear. Very popular in the marine aquarium trade in the UK, this species is not known to exist in the wild just yet; though based on it’s severe impact upon the Mediterranian ecosystem, it deserves a spot on this list nonetheless. Indeed, conservationists and anglers alike are predicting its spread into the wild in the very near future. Perhaps this addition to the list can be seen as a forewarning of things to come?

Half-Penny: aliens and interlopers

There are many words used to describe species which, through human intervention, have found themselves existing far outside of their historic, natural range. Terms such as invasives, aliens, invasive aliens and nonindigenous species are quite familiar; while a glance at social media often reveals myriad more unflattering phrases: pest, nuisance, menace, vermin – I particularly loathe the latter. Regardless of the terminology applied to them, however, such species have become a figment of daily life in present day Britain: intermingling with and, in some cases, out-competing many of our native creatures. Some are unwelcome, some are accepted and others are ignored entirely; though for many, myself included, aliens and interlopers have quickly become a fact of life around our respective local patches. So much so, in fact, that they appear rooted in the very foundation of the places we know and love. My local patch, Half-Penny, is no different.

Setting out with the express intent of documenting the variety of exotic species thriving, or merely surviving, within the wood, I arrived just before dawn – the bright yet deceivingly cold sunlight just beginning to percolate down to the woodland floor. Bouncing off the palmate leaves of Sycamore and transforming the carpet of native Butterbur and Ground Elder beneath into a mosaic of jaded and rejuvenated greens. Sycamore – a non-native species introduced by either the Romans or the Tudors, depending on the source, so familiar that is often hard to imagine the tree being anything other than a time-honored resident. One alien down.

Further into the wood, an assortment of plump, white berries shone by the side of footpath – a beacon of unfamiliarity, far removed from anything else found within the depths of Half-Penny. I am, of course, referring to the ivory fruits of Snowberry Symphoricarpos albus – a North American species which here, in my wood, has spread like wildfire, now representing the dominant shrub species across at least half of the site. An appealing species, boasting delicate pink flowers earlier in the year that, reluctantly, I have come to accept as a permanent feature of life here. Indeed, it would take a considerable effort to halt its creeping but clearly apparent advance.

Moving forward, the smell of Himalayan Balsam caught my attention long before first glimpse of the the sea of swaying pink blooms that dominates the mid-wood in late Summer. A species familiar to many that needs no introduction: balsam is a blight to native flora yet a handy source of nectar for various pollinators, many of which, today, could be seen hovering deftly around the bell shaped flowers. The internal jury is still out on this one; though less so on the small stand of Japanese Knotweed uncovered further into the tangle. A species which, due to a combination of education and personal experience, I find it hard to look upon with even a hint of appreciation. I doubt said stand will remain small for long, given the tendency of this species to spread like measles. It may have a hard job competing with the already established balsam, however. May the best (or worst) plant win.

Stopping briefly to admire the hulking frame of a Turkey Oak – a much more welcome invader which, year after year, provides a reliable source of delightfully hairy acorns for woodland residents to savor – my attentions soon turned to a yellow bloom protruding conspicuously from amid a riverside depression. Monkeyflower Mimulus guttatus, another invader of American origin which, rather oddly, is the county flower of Tyne and Wear. This species, much like the Turkey Oak, does not appear to be causing much of the problem in the wood; and like the oak with its comical, fuzzy fruit, provides a handy resource for local animals. Demonstrated by the Carder bee buzzing hastily between flowers as I watched, intrigued.

Less conspicuous than the botanical interlopers yet equally as prolific, it was not long before I caught sight of my first Grey Squirrel of the day. An unwelcome arrival which, more so than any other, cuts straight to my heart despite its altogether cute appeal. You see, during childhood visits to the wood, native Red Squirrels were a familiar sight, common even. A trend which lasted right up until 2013, when, to my surprise and distress, I sighted my first grey in the area. An ill omen of things to come later as the latter increased and the former decreased, fading from existence by 2016 – the same time as I began work as a Grey Squirrel control volunteer.

Grey Squirrels are one alien I find it hard to tolerate; not because I see them in a particularly negative light – they are rather endearing, in truth – but because of the damage done to a much-loved local species. I suspect this makes me a frightful hypocrite given my begrudging fondness for balsam and the plants impact upon native flora, though none of us are perfect. Though I wish we didn’t, we all place varying amounts of significance on certain species, often at the expense of others. It’s human nature.

Today I appreciate the squirrel for what it is, a highly adaptive and incredibly successful species. With more evidence of the rodents continued success in Half-Penny uncovered upon my departure. A pile of gnawed hazel shells: a small but stark testament to the changing nature of Half-Penny which, in spite of human interference, appears set to shift further in years to come.