“Super-slugs” are invading British gardens – and we don’t know how to stop them

Mmmmmm, slimy. Image: Xauxa Håkan Svensson.

The Daily Mail calls it a “slime wave”. The Sun calls them “an army”. Either way, both papers have reported 500bn slugs are set to invade British gardens, after a mild winter created perfect breeding conditions. The Conversation

So is the UK really about to be overwhelmed by slimy slugs? The simple answer is no, but there could be something far worse in store.

Headline numbers alone aren’t necessarily something to get in a lather over. A typical garden can contain several thousand slugs, and the “500bn” figure is derived from estimates of maximum numbers per area. In any case, slug numbers can rise and fall a great deal across time and space, in natural cycles, and even astonishingly dramatic increases are not always cause for concern. Like waves crashing against a beach, the rise is often transient and local – usually slug numbers will drop back to normal, with the disturbance hardly noticed beyond a few local gardeners.

What is more problematic is the progressive, sustained and perhaps less spectacular rise in numbers which, tsunami-like, is maintained for far longer, and spreads widely throughout the countryside. This is Britain’s real slug invasion. So what can we do about it?

The trigger seems innocuous enough in isolation: a few non-native slugs from continental Europe have accidentally been introduced. Several of these species have close relatives in the UK, so similar in fact that only specialists can tell them apart, and they can interbreed freely. Of course, many animals can create hybrids without presenting a threat, but what makes slugs different – and these hybrids so worrying – is their interesting and deviant sex lives.

This is a hybrid between a ‘Spanish stealth slug’ and the UK’s common black slug. Image: Les Noble/author provided.

Slugs are hermaphrodites, which means the same individual exists as both sexes; they first develop as males, before experiencing a true hermaphrodite phase to become female. This means they can dispense with normal mating requirements, and this is where the consequences of the difference between British and continental species becomes significant.

Why British slugs are different

When slugs colonised the UK after the last ice age, they found an island recently covered with ice sheets, where the biological diversity remained poorer than continental Europe. In these circumstances, the ability to self-fertilise was a good evolutionary strategy, one which ensured reproduction even when slug populations were devasated by harsh weather.

A downside of such continued close inbreeding (and mating with oneself is as inbred as it gets) is a rapid loss of genetic variability, and some British slug species eventually came to consist of almost genetically identical individuals. This meant they were more vulnerable to parasites and pathogens that could rapidly evolve to overcome their defences.

Meanwhile, in continental Europe, slugs were becoming more diverse, as balmier weather meant parasites and pathogens were a bigger issue than finding a mate. These slugs tended not to self-fertilise, and were genetically highly variable. This made at least some of them more resilient to attacks from parasites – a possibility not afforded to the inbred British slugs.

Echoes of these different past environments resonate in contemporary species. British slugs, adapted to a variable climate and dearth of mates, have fallen into the clichéd “No sex please, we’re British” mould, producing fewer, bigger eggs later in life by self-fertilisation. Continental slugs, meanwhile, adapted to resist rapidly evolving enemies. Their strategy is therefore to produce many smaller eggs earlier in life, which maximises genetic diversity and compensates for losing many individuals to infection.

The ‘Spanish slug’, one of Britain’s key invaders. Image: tviolet/creative commons.

These different adaptations weren’t an issue until humans disturbed the natural order by moving slugs back and forth as stowaways in commercial produce. As a result of this, we’ve seen widespread breeding between British and continental species. These new hybrid “super-slugs” are highly fertile, and their genetically diverse offspring are adapted to cope with both the British climate and parasites and pathogens, most of which remain in continental Europe anyway.


Fighting the slug invasion?

Legislation aimed at environmental protection has led to the EU banning commercial use of molluscicides (pelleted chemicals which poison slugs but cause collateral damage to other wildlife). Instead, the emphasis is on using natural enemies like nematode worms, though these are generally ineffective against the larger invasive hybrids.

Nonetheless, the increased slug biomass could still host important veterinary or agricultural parasites and pathogens, spreading more plant and animal diseases. Remarkably, despite their obvious presence in our gardens, we remain startlingly ignorant of the fundamental biology of slugs; evidenced by recent work which increased the number of identified British species by more than a fifth.

So where are we going with this phenomenon? Studies have already found invasive slugs and snails can destabilise ecosystems and reduce biodiversity in the US and Scandinavia. Something similar is happening here in the UK.

The good news is that our research suggests population sizes do eventually begin to decline, after 30 to 40 years. The ecosystem may eventually rebound from this slug invasion, but it remains to be seen how long it will take and what the lasting effects will be for the spread of diseases, ecosystem services, or British biodiversity.

Leslie Noble is a reader in zoology at the University of Aberdeen.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

The Réseau Express Métropolitain: the multi-billion dollar light rail project Montreal never asked for

Montreal from the summit of Mont Royal. Image: Getty.

The Réseau Express Métropolitain (REM) is the 67-kilometre, C$6.3bn light rail project Montreal never asked for.

It is the single largest transit project in Montreal in half a century. Not since the construction of the Métro has there been as bold a proposal: an entirely new mass-transit system that would have the effect of radically altering the city’s urban landscape.

Conceived, planned and costed by the Province of Quebec’s institutional investor, the Caisse de dépot et placement du Québec (CDPQ), the REM is currently under construction and slated to become operational between 2021 and 2023.

Once completed, it is supposed to provide high-frequency, intermediate-volume light-rail service on a regional level: connecting suburbs with the city centre along three axes and linking Montreal’s central business district with its international airport.

The REM may even connect to an as-yet unbuilt baseball stadium, or be extended as far as Quebec City, some 400km away, to replace the existing commuter rail network. Indeed, the REM has been strongly endorsed – by both the federal and provincial governments that back it – as a panacea for all of Greater Montreal’s transit and traffic congestion problems.
Since it was first proposed in 2015, the REM has been championed above all else as a guaranteed-to-succeed “public-public partnership”. A win-win, where various levels of government cooperate and coordinate with an arm’s-length government agency to produce much-needed new transit and transport infrastructure.

Unlike the more commonly known public-private partnership (of which there are some notable recent failures in Quebec), the obvious insinuation is that – this time – there’s no private interest or profit to worry about.

PR aside, the pension funds managed by the CDPQ are private, not public, wealth. The CDPQ’s entire raison d’etre is to profit. It has even gone to the lengths of “mandating” the REM to provide it an annual profit of about 10 per cent, a cost to be assumed by the governments of Quebec and Canada in the event the REM isn’t profitable.

The law that has made the REM possible has other interesting components. The REM is legally distinct from and superior to other public transit agencies and the extant regional planning authority. It has exclusive access to publicly-funded transit infrastructure. There’s even a “non-compete” clause with the city’s existing mass transit services, as well as special surtax on all properties within a 1km radius of each of the 26 proposed stations.

This latter element takes on a new dimension when you consider the CDPQ’s real-estate arm, Ivanhoé-Cambridge, has a near total monopoly on the properties surrounding the future downtown nexus of the REM, and is invested in suburban shopping centres that will soon host REM stations.

It seems that Montreal isn't so much getting a new mass transit system as a pension fund is using a new transport system to stimulate growth in a faltering if not moribund commercial and residential property sector.

Quebec’s public pensions have historically invested in suburban sprawl. As this market becomes increasingly untenable, and populations shift back towards the city centre, the REM is supposed to stimulate growth in “transit-oriented developments” centred on its future stations. The new surtaxes are likely intended to force sales of land for immediate redevelopment, so that new homes are ready to move into as soon as the system becomes operational.

It’s important here to remember that the city of Montreal wasn’t given several billion dollars by the government with which to spend developing its mass transit system. Rather, Quebec’s former premier asked the CDPQ to come up with a way to integrate several long-standing yet unrealized transit proposals. These included a light-rail system over Montreal’s new Champlain Bridge, an express train to Pierre Elliott Trudeau International Airport, and a dedicated commuter rail line for the Western suburbs. It was the CDPQ that proposed a fully-automated light-rail system that would use existing technology as well as some of Montreal’s extant railway infrastructure as an inexpensive way of uniting several different projects into an assumedly more efficient one.

So far so good. Cities need more mass transit, especially in the era of climate change, and Montreal contends with regular congestion both on its roadways and various mass transit systems. Moreover, access to the city’s already generally-high quality public transit systems is an important driver of property values and new residential development.

Considering the evident need for more transit, the REM theoretically provides an opportunity to kill several birds with one stone. Better still, the REM will in all likelihood stimulate the transit-oriented developments and re-urbanisation necessary for a more sustainable future city.

A map of the proposed network, with metro lines in colour and commuter rail in grey. Click to expand. Image: Calvin411/Wikimedia Commons.

The REM is the business “test case” on which two new government entities are based; the CDPQ’s infrastructure development arm, and the Canadian government’s infrastructure development bank.

The REM is also intended to stimulate economic activity in important economic sectors – such as engineering, construction and technology – that could soon be in high-demand internationally. Both the governments of Quebec and Canada see tremendous value in the economic potential of infrastructure mega projects at home and abroad.

This aside, the actual development of the REM has been complicated by what appears to be a bad case of over-promising and under-delivering, at least in terms of how seamlessly it could be integrated into the city’s extant transit and transport systems.

Though the train as originally conceived was intended to use an existing electrified railway line as the backbone of the network, it now appears that the REM cannot in fact be adapted to the line’s current voltage. The entire line, and the tunnel it passes through, requires a thorough overhaul, something that had last been completed in the mid-1990s. The new electrification, as well as the reconstruction of the tunnel, will cut it off from the regional commuter rail network. Rather than have different types of rail systems share existing infrastructure, the REM will force the premature (and unnecessary) retirement of a fleet of high-volume electric trains.

Consider that while the REM will connect the city with its international airport, it’s not planned to go just one kilometre farther to connect the airport with a major multi-modal transit station. Dorval Station integrates a sizeable suburban bus terminus with a train station that serves both regional commuter rail as well as the national railways network.

It’s difficult to understand how and why such an obvious and useful connection wasn’t considered. Given long-standing interest in high-speed and/or high-frequency rail service in Canada, La Presse columnist François Cardinal has noted that a REM connection between airport and a likely future rail hub would extend access to international air travel far further than just downtown Montreal.


The REM was also supposed to integrate seamlessly into the Montreal’s built environment, its promoters insisting construction could be completed with minimal inconvenience to current transit users. By the end of this year, REM-related construction will force a two-year closure of Montreal’s most-used commuter rail line, and sever the most recently-built rail line off from the transit hubs in the centre of the city. Tens of thousands of commuters throughout the Montreal region will be forced to make do will already over-saturated bus and métro service.

Though public consultations revealed these and other flaws, concerns raised by the public, by professionals and even some politicians were largely ignored. The REM also failed its environmental assessment. The provincial agency responsible for such evaluations, the BAPE, stated baldly that the project wasn't ready for primetime and lambasted the CDPQ’s lack of transparency. In turn, the BAPE was accused of exceeding its mandate. The REM made a similarly poor impression, with transit users groups, architects and urban planners criticizing the project in whole and in part.

The main points of contention are that the REM won’t do much in the short term to alleviate congestion across the city’s existing – and comparatively expansive - mass-transit network. Quite the opposite: it is already beginning to exacerbate the problem.

Because the REM was conceived without the involvement of either the city’s main transit agency or the regional transit planning authority, its progress is hampered by a wide-variety of problems that would otherwise likely have been planned for. And because it’s a mass-transit solution to what is primarily a political consideration, the REM will provide higher-frequency service of dubious necessity to the city’s low-density suburban hinterland, much of which already has ample commuter-focused transit service. The high-density urban-core, which is most in need of transit expansion, will benefit perhaps least of all.

While it’s unlikely the REM will fail outright, it’s also unlikely to stimulate much new interest in using mass-transit services: it will first have to win back those who may abandon mass-transit while the REM is being built. Providing higher-frequency service to suburbia is the kind of thing that sounds good in theory, but doesn’t respond to commuters’ actual needs. Arguably the REM’s best feature – its real-estate development potential – has been somewhat obscured from public view because of obvious conflicts of interest. The REM’s limitations – and there are many – will for the most part only become known once the system is operational, at which point it will be too late.

The REM provides interesting theoretical avenues worthy of exploration – particularly the potential relationships between new transit development and how it may stimulate new growth in the housing sector. But building a new transit system – especially one this large and complex – ultimately requires the fullest possible degree of cooperation; with transit users, extant transit agencies and regional planning bodies.

Ignoring the recommendations of experts, the public and government assessment agencies for the sake of expediency is never a wise idea. When it comes to designing and implementing the mass-transit systems of the future, the needs, wants and opinions of users must be paramount. In Montreal, it appears as though they were an afterthought and an inconvenience.

Whether Montrealers will be able to vote with their wallets remains to be seen. As things now stand, it appears the city’s bus network will be forced to integrate with it, removing redundancy and ensuring that users won’t have much choice but to use it.

It’s difficult to imagine how forcing people to use a transit system they never asked for will encourage greater use.