New York: where the streets are paved with hot dogs, donuts, burgers – and hungry insects

If you don’t finish it the ants will. Image: Rowan Peter, CC BY-SA.

New York is one of many cities whose mythical allure claims that the streets are paved with gold. Sadly, you are more likely to be treading on – or at least wading through – the remains of burgers, hot dogs, sweets, cookies, fries and more unmentionable sources of nutrients. Yet in among all that detritus is an awful lot of energy, a resource that could underpin a complex ecosystem.

Food webs are a staple of ecology research, but usually explored in rain forests and coral reefs, ponds and savannahs. However a team at North Carolina State University has recently turned its attention to the much more dangerous terrain of Manhattan to find out if the insects living on and under the streets clear up a significant amount of the food litter – and whether the diversity of species makes any difference. Their results are published in the journal Global Change Biology.

The precise relationship between resources and the diversity of flora and fauna in ecosystems has been the subject of intense research ever since the coming of the word “biodiversity” in the late 1980s. Ecologists were challenged to explain the role of species: does it matter how many there are, does the number of species affect the way ecosystems work, what do all these species do for us?

If insects could evolve to exploit the modern city, they might end up like these pizza beetles. Image: Mike Jeffries.

All this activity drives the natural ecosystems which keep us alive. Ecosystems are more productive, efficient and resilient the more species they contain, perhaps because different species carry out complementary roles or, however unwittingly, benefit the activities of others.

Hitting the streets

The North Carolina team set out to test whether the diversity of invertebrate street life affected the removal of food that had suffered “improper disposal” (a charming politeness runs through the whole study) in the parks and elongated traffic islands of Manhattan.

To audit the pavement biodiversity, the team collected insects from among the leaf litter, with additional forays into other areas in search of ants. The rate of food clear-up was measured by putting out potato chips, cookies and hot dogs and seeing how much was left the following day. Some of the food was protected by wire mesh, others not – so that larger creatures such as rats and pigeons could get in too, to allow for their impact. The precise brands of crisp, cookie and hot dog are detailed, each cut up into more appetising chunks.

This is important, allowing experimental replication with street food around the world. For example in Britain the late-night kebab might be a significant bio-geographical variation. The rate of food clear-up was compared to the overall diversity of invertebrates and the precise mix of species. Sadly, nowhere do the team members outline how they explained any of their activity to passing policemen.

Garbage guzzlers

The speed with which food was removed proved startling. In the first run of the experiment using small chunks of food, 59 per cent was gone within 24 hours. A second run using larger portions resulted in a 32 per cent loss within a day. Whole cookies and chips, gone; chunks of hot dog vanished.

The insect life on the traffic islands consumed supplies two to three times faster than the inhabitants of the parks. Life in the fast lane perhaps, or maybe the park life was more used to ice creams and sandwiches. In either locality, hot dogs were preferred to the light snacks.

In total the insects from the medians and traffic islands of two long Manhattan streets – Broadway and West St – could remove the equivalent of 600,000 potato chips per year. This could become a standard measure of invertebrate junk food ecosystem services.

Pavement ant: a hot dog’s worst nightmare.AntWeb, CC BY

The overall conclusion is that our invertebrate neighbours in the city make a notable contribution to the removal of litter. However the food clear-up was not affected by the diversity of species. More important was the presence of one species of ant, the perfectly named pavement ant, Tetramorium caespitum. Two to three times more food was removed where these particular ants were present.

There is something particularly pleasing about it being the pavement ant. Not just the name; this ant is not a native New Yorker, but an immigrant from over a century ago, probably coming from Europe to the Big Apple.

Urban wildlife is often rather overlooked as a sorry mix of second-rate left-over habitats and dodgy aliens. However the city represents a whole new habitat, likely to become ever more widespread; a zoopolis, with a distinct and fascinating ecology. Where the streets are paved with last night’s food, these ants have certainly found their niche.The Conversation

Mike Jeffies is a teaching fellow in the ecology department at Northumbria University, Newcastle. 

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


Leeds is still haunted by its pledge to be the “Motorway City of the Seventies”

Oh, Leeds. Image: mtaylor848/Wikimedia Commons.

As the local tourist board will no doubt tell you, Leeds has much to be proud of: grandiose industrial architecture in the form of faux-Egyptian temples and Italian bell-towers; an enduring cultural legacy as the birthplace of Goth, and… motorways. But stand above the A58(M) – the first “urban motorway”  in the country – and you might struggle to pinpoint its tourist appeal.

Back in the 1970s, though, the city council was sufficiently gripped by the majesty of the motorways to make them a part of its branding. Letters sent from Leeds were stamped with a postmark proudly proclaiming the city's modernity: “Leeds, Motorway City of the Seventies”.

Image: public domain.

During the 1960s, post-war optimism and an appetite for grand civic projects saw the rapid construction of motorways across England. The construction of the M1 began in 1959; it reached Leeds, its final destination, in 1968. By the early 1970s the M62 was sweeping across Pennines, and the M621 loop was constructed to link it to Leeds city centre.

Not content with being the meeting point of two major motorways, Leeds was also the first UK city to construct a motorway through the city centre: the inner ring road, which incorporates the short motorway stretches of the A58(M) and the A64(M). As the council put it in 1971, “Leeds is surging forward into the Seventies”.

The driving force behind Leeds' love of motorways was a mix of civic pride and utopian city planning. Like many industrial cities in the North and Midlands, Leeds experienced a decline in traditional manufacturing during the 1960s. Its position at the centre of two major motorways seemed to offer a brighter future as a dynamic city open for trade, with the infrastructure to match. In response to the expansion of the roads, 1970s council planners also constructed an elevated pedestrian “skywalk” in an attempt to free up space for cars at ground level. Photos of Leeds from that time show a thin, white walkway running through blocky office buildings – perhaps not quite as extensive as the futuristic urban landscape originally envisaged by planners, but certainly a visual break with the past.

Fast forward to 2019 and Leeds’ efforts to become a “Motorway City” seems like a kitsch curiosity from a decade that was not always known for sustainable planning decisions. Leeds’s historic deference to the car has serious consequences in the present: in February 2019, Neville Street – a busy tunnel that cuts under Leeds station – was found to contain the highest levels of NO2 outside London.

City centre planners did at least have the foresight to sink stretches of the inner motorways below street level, leaving pedestrian routes largely undisturbed. Just outside the centre, though, the roads can be more disruptive. Sheepscar Interchange is a bewildering tangle of arterial roads, Armley Gyratory strikes fear into the hearts of learner drivers, and the M621 carves unsympathetically through inner-city areas of South Leeds with pedestrian access restricted to narrow bridges that heighten the sense of a fragmented landscape.


Leeds inner ring road in its cutting. Image: author provided.


The greatest problem for Yorkshire's “Motorway City” in 2019, however, is not the occasional intimidating junction, but the complete lack of an alternative to car travel. The dire state of public transport in Leeds has already been raised on these pages. In the early 20th century Leeds had one of the most extensive tram networks in the country. The last lines closed in 1959, the same year construction began on the A58m.

The short-sightedness of this decision was already recognised in the 1970s, as traffic began to build. Yet plans for a Leeds Supertram were rejected by successive Conservative and Labour governments unwilling to front the cost, even though smaller cities such as Newcastle and Sheffield were granted funding for light transport systems. Today, Leeds is the largest city in the EU without a mass transit system. As well as creating congestion, the lack of viable public transport options prevents connectivity: the city's bus network is reasonable, but weaker from East to West than North to South. As a non-driver, I've turned down jobs a short drive away that would be a logistical impossibility without a car.

Leeds' early enthusiasm for the motorway was perhaps premature, but there are things we can learn from the 1970s. Whatever else can be said about it, Leeds' city transport strategy was certainly bold – a quality in short supply today, after proposals for the supertram were watered down to a trolleybus system before being scrapped altogether in 2016. Leeds' rapid transformation in the 1960s and 70s, its grandiose visions of skywalks and dual carriageways, were driven by strong local political will. Today, the long-term transport strategy documents on Leeds City Council's website say more about HS2 than the need for a mass transit system within Leeds itself, and the council has been accused of giving up the fight for light rail and trams.

Whilst central government's refusal to grant funds is the greatest obstacle to Leeds' development, the local authority needs to be far more vocal in demanding the transport system the city deserves. Leeds' desire to be the Motorway City of the Seventies might look ludicrous today, but the political drive and utopian optimism that underpinned it does not.