Today we have the first contribution of the year by Athayde Tonhasca Júnior: one of his patented word-and-photo stories. His text is indented, and you can enlarge his photos by clicking on them.
How beauteous mankind is! O brave new world,
That has such people in’t.
—William Shakespeare, The Tempest
Mr McGuire: I want to say one word to you. Just one word.
Benjamin: Yes, sir.
Mr McGuire: Are you listening?
Benjamin: Yes, I am.
Mr McGuire: Plastics.
Mr McGuire was prescient in his advice to young Benjamin Braddock about his career options (The Graduate, 1967): the plastics industry has since expanded to levels unimaginable then. Cheap, versatile, resistant and durable, plastic products are essential in today’s society. They are everywhere. So, unsurprisingly, they are an ever growing environmental problem: land, waterways and the oceans are stuffed with discarded plastic.
Plastic rubbish is a blight on the landscape, but some birds and mammals have taken advantage of this abundance of material. Squirrels and opossums have learned to use straws, string and plastic bags for nest building; plastic fragments were present in about 14% of surveyed nests of the brown booby (Sula leucogaster), a seabird found around the world. So, diligent nest builders such as leaf-cutter bees (genus Megachile) were bound to join this team of opportunists.
Most leaf-cutter bees cut pieces of leaves or petals to build their nests; some use mud, pebbles or resin as construction materials. These bees usually nest in sheltered natural cavities such as burrows, crevices and hollow twigs. They are important pollinators, and a few species have been reared commercially for crop production, such as the alfalfa leaf-cutter bee (Megachile rotundata).
A Megachile centuncularis at work. This is one of seven megachilid bees in Britain © Line Sabroe Wikimedia Commons:
A leaf-cutter bee nest © Subbu Subramanya, Wikimedia Commons:
In Ontario, Canada, alfalfa leaf-cutter bees have been creative and resourceful by using pieces of polyethylene-based shopping bags as a building material. Another local species, the bellflower resin bee (Megachile campanulae), constructs nests with plant resins instead of leaf and stem segments. It has no use for plastic bags, but polyurethane-based sealants, which are applied to the exteriors of buildings, offer a handy and abundant alternative. Some bellflower resin bees mixed this plastic product with natural resins to build their nests.
Brood cells partially constructed with polyethylene plastic bag fragments (L,) and polyethylene resin © MacIvor & Moore, 2013. Ecosphere 4: 1-6
Rural areas are not exempt from the plastic deluge. In the Argentinian countryside, bits of greenhouse covers, agrochemical containers, fertilizer bags and irrigation hoses combine with the ubiquitous shopping bags to deface the landscape. One bee, possibly an alfalfa leaf-cutter bee, took advantage of this clutter to do away with leaves or petals completely: she built an entire nest with pieces of two types of plastic.
A plastic nest of Megachile sp. built in a nest trap © Allasino et al., 2019. Apidologie 50: 230–233:
We don’t know whether plastics have any effect on leaf-cutter bees. They may be neutral, or even beneficial; plastics may act as a barrier against fungi and parasites, which are important mortality factors for solitary bees. On the other hand, these impermeable materials may trap water and thus increase the brood’s susceptibility to diseases.
By using plastics, bees have demonstrated their ability to identify alternative and convenient resources, and to adjust to changes in their environment. All the same, plastic nests are another troubling sign of a world living in the Anthropocene. From the Greek anthropos (man) and cene (new or recent), this unofficially labelled geological epoch applies to Earth’s history since humans started to have a significant impact on climate and ecosystems. It’s a new world of mass extinctions, deforestation, pollution, fossil fuels, and climate change. Perhaps leaf-cutter bees can adapt and even flourish in this world. We may do the same. Or not.
In 1926, the British government’s Central Electricity Board set out to create a nationwide electrical grid to bring cheap power for everyone. This was the biggest building project that Britain had ever seen, and soon steel pylons and transmission lines began popping up all over the landscape. And many people didn’t like what they saw. In 1929, Rudyard Kipling and John Maynard Keynes co-signed a letter to The Times objecting the construction of pylons, noting they were ‘the permanent disfigurement of a familiar feature of the English landscape.’ The pylon’s designer, architect Sir Reginald Blomfield, fired back: ‘Anyone who has seen these strange masts and lines striding across the country, ignoring all obstacles in their strenuous march, can realise without a great effort of imagination that [they] have an element of romance of their own. The wise man does not tilt at windmills – one may not like it, but the world moves on.’
You may side with Kipling and Keynes or Blomfield in this aesthetics vs utility debate, but transmission lines are here to stay, for a while at least. The British grid of high-voltage lines from power stations alone runs for ~25,000 km; adding to that several thousand kilometres of regional networks, power lines have become part of our landscape.
Transmission corridors, similar to roadsides and railway embankments, are routinely mowed, clear-cut or treated with herbicides to prevent the encroachment of trees and dense vegetation. These practices are viewed as necessary evils by the public and some conservationists; but, with the right touch, they create opportunities for bees and other pollinators.
In ecology, ‘succession’ is the process by which a natural area changes after a disturbance or following the initial colonization of a new place. In terrestrial habitats, early succession refers to the period before they become enclosed by trees’ canopy. Weedy areas, grasslands, old fields or pastures, shrub thickets and young forests are all examples of early successional habitats. And so are transmission corridors, where maintenance crews prevent succession from reaching its equilibrium point or climax by cutting down the vegetation.
Plant succession © CNX OpenStax, Wikimedia Commons:
It turns out that habitats in the early successional stages are excellent for bees. These areas offer a steady supply of nectar and pollen over much of the year, as opposed to forested areas where blooms peak in spring and are limited by the shaded canopy from midsummer on. The large majority of bee species nest in the ground; they need patches of bare soil of the right texture and moisture levels, and close to their food plants. Successional habitats are just the right place for this combination of features. So it’s not surprising that bee abundance and species richness decreases with increasing forest cover.
Lots of flowers, nesting/hibernation sites & sunshine: perfect for bees © Mick Garratt, Wikimedia Commons:
In the north-eastern United States, energy companies have been maintaining power lines under Integrated Vegetation Management (IVM) since the 1950s with the objective of protecting the grid while providing habitat for threatened plants and animals. It sounds fancy, but essentially IVM comprises five-year cycles of selectively killing trees (mechanically or with herbicides), with no mowing or widespread spraying of herbicides. These simple techniques create a mosaic of meadow, herbaceous plants and shrubs, which have proved to be good for many reptiles, amphibians, birds, small mammals, and bees. A comprehensive survey along 140 km of a transmission line in New England revealed that the sunny, open corridors held nearly 10 times the number of bees and twice the number of bee species as compared to adjacent forested areas. Not only that, about half the known species for the region, including some rarities, were found in the survey (Wagner et al., 2019. Biological Conservation 235: 147-156).
A power line corridor, great habitat for bees © Mark Nenadov, Wikimedia Commonns:
Not everybody likes the sight of a transmission line. But these ugly and gloomy steel towers and cables can be turned into pollinator and wildlife havens. All it takes is goodwill and some imaginative work. The lights will stay on, and there will more bees around.
The Milky Way galaxy has awed civilizations and inspired many philosophical thoughts about mankind’s insignificance, our place in the big scheme of things, the fleeting nature of life, and what it’s all about. But if young Europeans or Americans are asked to share their impressions about the Milky Way, responses are likely to be limited to a shrug or a puzzled look: about 60% of Europeans and 80% of North Americans have never seen it. When Los Angeles went through a blackout in 1994 because of an earthquake, emergency services received several calls from nervous citizens about a giant, strange, silvery cloud in the dark sky. These Angelinos were seeing the Milky Way for the first time.
The Milky Way, unseen by many © Oliver Griebl, Wikimedia Commons:
As the human population increases and concentrates more and more in cities, the world becomes more illuminated. Artificial light at night (ALAN) is an ever-growing phenomenon because of the lighting of streets, parking lots, roads, buildings, parks, monuments, airports, stadiums – basically any manmade structure. This artificial light is scattered into the atmosphere and reflected back, particularly by clouds, creating a nighttime sky luminance known as ‘sky glow’. Excessive illumination and artificial sky glow spread way beyond urbanized areas, essentially contaminating the whole landscape with light: nighttime darkness is disappearing.
Glow in the sky from Helsinki seen in Estonia © Bilovitskiy, Wikimedia Commons:
Light pollution is an ecological disturbance with multiple consequences. ALAN disrupts natural day-to-night rhythms such as singing and migration of birds, the activity period of small mammals, mating of frogs, nesting of bats and the orientation of sea turtle hatchlings. There is increasing evidence that humans are also sensitive to ALAN: it affects our circadian rhythm (the sleep–wake cycle repeated approximately every 24 hours), resulting in irregular hormone production, depression, insomnia and other maladies.
Insects couldn’t be immune to the effects of ALAN since much of their behaviour is dependent on light. We don’t know how insects see the world, but they recognize forms, detect movements and discern colours based on lighting patterns. Insects can monitor the position of the sun by the polarization of light, so they can navigate with precision. Light detection helps them to keep track of the photoperiod (day length), which is fundamental to preparing for the winter months.
Many beetles, flies, lacewings, aphids, dragonflies, caddisflies, wasps and crickets are drawn to light, but moths’ compulsive and apparently suicidal attraction to lightbulbs or flames is the most familiar case of positive phototaxis (moving towards a light source) among insects. Moths are important pollinators, so naturally their possible vulnerability to killer lights is a matter of concern.
A fatal attraction © Fir0002, Wikimedia Commons:
It turns out that moths’ fatal attraction doesn’t seem to be that fatal because they are only drawn to light at relatively short distances. A few moths come to a blazing end, but most of them are beyond light’s dangerous pull. This is not to say that moths are safe from ALAN. When the night is not sufficiently dark, egg-laying and production of sex pheromones are inhibited for some species, so that their reproduction is affected. Also, the window of time for courtship and mating can be severely reduced. Light pollution interferes with moths’ perception of colours and shapes, signals necessary for flower location. It also makes them more vulnerable to parasites and predators, either because they are easier to find, or their defence mechanisms (e.g., bat avoidance manoeuvres) are less effective in over-illuminated environments.
Light pollution disturbs many aspects of moths’ physiology and behaviour, although we can’t tell whether whole populations are being harmed: not all species respond equally, and there are many variables to be considered about the light source, such as wavelength, intensity, polarization and flicker. But from the little we know, excessive illumination can be added to the list of pressures on our moth fauna and consequently on pollination services.
At a time of growing concern about global warming, light pollution may sound like a secondary problem. But the more researchers look into it, the more they learn that this is a serious environmental threat. And while sorting out the climatic mess will be tricky and complex, the light pollution problem is relatively easy. The first, obvious and straightforward measure is to turn off unnecessary lights. When illumination is needed, it could be dimmed, shielded or limited to specific areas such as pavements or roads. Light dimming is good for the environment and for the economy too. When in 2018 the city of Tucson, USA, converted nearly 20,000 of their street lights to dimmable LEDs, £1.4m were saved from its annual energy bill.
Preserving and protecting the nighttime environment is an important but neglected aspect of conservation. A darker world would benefit moths and other species, and it would be good for us as well. We could sleep better or go stargazing again.
World map of light pollution: colours show intensities of sky glow from artificial light sources © David Lorenz, Wikimedia Commons: