Greenland has been in the news a bit lately. From Huskies seemingly walking on water, to temperatures soaring to 20℃ above average for the time of year, to predictions of the vast ice sheet being lost entirely, what is going on?
At its most simple: ice melts when it gets too warm.
Of course, some ice melts every time summer rolls around, but the amount of Arctic ice that melts each summer is growing, and we’re waiting to see whether this turns out to be a record-breaking year for Greenland ice melt.
No part of the planet is free from the impacts of human-caused climate change. But Greenland, and the Arctic more generally, is experiencing the impacts particularly severely. Temperatures in the planet’s extreme north are rising twice as fast as the global average.
Greenland is warming so rapidly because of what climate scientists refer to as a “positive feedback”. Despite the name, these are not good. A better term might be “climate change amplifier”.
The Arctic has many “positive feedbacks” or “amplifiers” that worsen the effects of climate change here. For example, as snow and ice begin to melt, the surface darkens, allowing it to absorb more heat and thus melt even more.
This effect is most dramatic when snow and ice are lost completely, as in the case of the dramatic loss of the sea ice covering the Arctic ocean. Arctic sea ice loss is one of the major factors that explains why the Arctic is warming so much faster than the rest of the planet.
Another worrisome characteristic of climate change in the Arctic is the potential for ice melt to accelerate. The temperature threshold at which ice begins to melt means that once the climate has warmed enough to start melting ice, any further warming will rapidly cause an even larger amount of melting to occur. That is the reality beginning to play out in Greenland.
Beginning of the 2019 summer melt season
Last month, ice melt across the surface of Greenland made headlines. Surface melting spiked rapidly and was unusually strong for June. Melting was most intense around the edges of the Greenland ice sheet, and about 40% of the entire ice sheet surface was affected to some extent.
Greenland ice melt is typically very irregular during each summer, spiking as weather systems bring warm air masses over the ice sheet. Given this variability, it is not yet clear whether 2019 is going to be an unusually bad year for melting over Greenland – and whether it will rival the worst year on record, 2012, when the entire surface of the ice sheet experienced melting.
But what is very clear from observations since the 1970s (and completely consistent with simple physics) is that as the Arctic climate warms, the Greenland summer melt season is starting earlier, lasting longer, and becoming more intense.
Samples of older ice from inside Greenland’s ice sheet paint an even clearer picture of the changes that climate warming is causing. The amount of summer melting first began to increase in the mid-1800s, not long after human-driven climate warming began. Summer melt over the past two decades has reached levels roughly 50% higher than before the Industrial Revolution, and the speed of ice loss from the Greenland sheet has increased nearly sixfold since the 1980s.
Choices for the future
An ice sheet has existed on Greenland for millions of years. But the geological timescales of ice sheet growth and renewal are vastly outpaced by the human-caused changes we see today.
A study published in June this year, at the same time surface melting of the ice sheet was spiking, predicts that if human greenhouse emissions continue unabated, by the end of this century ice loss from the Greenland ice sheet could see the ocean rise by up to 33cm.
If all of the Greenland ice sheet were to melt, global sea level would rise by more than 7 metres. According to the same study, that could potentially happen within 1,000 years.
The evidence is abundantly clear: the rising temperature of the planet is causing more Arctic ice to melt during the northern summer. We cannot avoid further ice loss in coming decades, and people and ecosystems will have to adapt to this.
But there is still a window of opportunity to avoid the worst impacts of future climate change in the longer term. The evidence tells us that the only way to prevent the destruction of the Greenland ice sheet, and multi-metre rises in global sea level, is to make rapid, deep cuts to greenhouse gas emissions. That is a choice we still have a chance to make.
Have you ever seen a fairy? They exist, and may very well be in your garden. But you would need a high-powered microscope to spot the dainty creatures.
Fairy wasps (family Mymaridae) are tiny, feathery-winged parasitoid wasps. They’re often called fairy flies, which is a misnomer. The Mymaridae family includes the smallest known insects in the world. Most species are less than 1mm long – smaller than the average pinhead.
But two species in particular have the record for being the smallest insects in the world. Measuring 0.15-0.19mm, the smallest recorded winged insects are female Kikiki huna.
Not much is known of K. huna’s ecology, but the species was first discovered in Hawai’i (the scientific name is made from Hawaiian words for “tiny bit”). Since then, specimens have been recorded from Western Australia and South and Central America, suggesting the species could be distributed much more widely.
In 2013, another closely related species was discovered in Costa Rica and named Tinkerbella nana, after Peter Pan’s fairy friend.
The smallest known insect of all, at around 0.13mm, is a wingless male specimen of another fairy wasp, Dicopomorpha echmepterygis, found in the United States. Many insect species are sexually dimorphic, meaning males and females can look so different they may be confused as different species. For this fairy wasp, females are much larger than the record-breaking males, and have wings.
Eggs in eggs, wheels within wheels
All fairy wasp larvae are parasites. Adult females search for the eggs of other insects in sheltered places, such as under leaves or in leaf litter. When she finds a stash, she lays her own eggs inside the other eggs – an indication of just how tiny these wasps are! The wasp larva uses the nutrients from the egg to develop, killing the other insect in the process, before emerging through a tiny hole in the egg surface. The BBC captured this process in mesmerising underwater footage in 2017.
Adults only live for a couple of days to reproduce and start the cycle again. In fact, some males never leave the egg they develop in – as soon as they emerge from their own egg within an egg, they mate with a female and die.
Despite their diminutive size, fairy wasps pack a punch when it comes to impact. Their dependence on other insects to complete their life cycle means they play an important role in controlling populations of many other insects.
Scientists don’t think these wasps have strong preferences about their host species, which means they seem to pick whatever eggs are available. But very little is known of the ecology of most species, so it is hard to know for certain.
Most of the known records of fairy wasps have emerged from eggs of Hemiptera species, the group of sucking bugs that includes planthoppers and aphids. But other hosts are known to include thrips (Thysanoptera), beetles (Coleoptera), and psocid (Psocoptera).
The smallest insect in the world, D. echmepterygis, was reared from eggs of a psocid, or barklouse species – another group of small insects that is often overlooked. Barklice and booklice, also called psocids, are in the order Psocoptera; barklice usually feed on lichen and algae on tree trunks, while their cousins the booklice are often found feeding on mould inside book bindings in old libraries.
Other fairy wasp species have become valued for their important role as biological control agents in agricultural systems. Mymarids can control many damaging economic pests, including the glassy-winged sharpshooter, and weevil and sucking bug pests of eucalypt plantations. Many other associations remain to be discovered.
Fairy wasps are a fascinating example of how much biodiversity is still undiscovered. With so much focus on larger, or more charismatic species, the tiny world of the smallest animals on Earth goes by unnoticed.
We still have much to learn about the ecology and life history of minuscule fairy wasps. Most of us would walk past one nearly every day without noticing. But we can support them without seeing them. Like many other flying insects, adults need sugar from floral nectar or insect honeydew for their energy.
This means that encouraging flowering plants to grow in and around crop fields can help production. These wild floral resources support populations of many beneficial insects, including fairy wasps, making them more effective as biological control agents. And, just like many other beneficial insects, pesticides can kill fairy wasps, or make them less effective at controlling other pests.
The same principle goes for gardens. Next time you find a pesky insect herbivore munching on your plants, consider an experiment: let them be and see how long it takes before fairies have moved into the bottom of your garden.