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Animals with white winter camouflage could struggle to adapt to climate change

Animals that turn white in the winter to hide themselves in snowy landscapes could struggle to adapt to climate change, research suggests.

A new study finds that declining winter snowfall near the Arctic could have varying effects on the survival of eight mammal species that undergo a seasonal colour moult from summer brown to winter white each year.

Species most at risk of standing out against the snow include mountain hares, snowshoe hares and short-tailed weasels. Without blending into the background, these animals could find it harder to hunt prey or hide from predators.

However, there are some parts of the northern hemisphere where colour-changing mammals could have a better chance of adapting to climate change, the study finds.

These “rescue” hotspots, which include northern Scotland and parts of North America, should be protected by conservationists to give colour-changing animals the best chance of adapting to future climate change, the lead author tells Carbon Brief.

Turning white

Visual camouflage is a vital tactic used by both predatory animals, who must hunt while avoiding detection, and their prey, who must hide to avoid being eaten.

But in parts of the northern hemisphere, the changing of the seasons offers a unique challenge to those trying to camouflage with their surroundings.

In winter, when the landscape is snowy and barren, animals with white colouring find it easiest to blend in. However, when spring arrives and snow is replaced with brown soils and growing vegetation, those with mottled brown colouring tend to find it easier to escape detection.



One solution to this problem, used by a range of animals, is to undergo a seasonal molt from brown to white each year.

Scientists have recorded 21 mammal and bird species using this colour-changing tactic, including the Siberian hamster, the collared lemming and the willow ptarmigan.

The new study, published in Science, focuses on how climate change could alter the survival chances of eight of these species.

Climate change is causing a decline in winter snow cover in Arctic regions, along with the earlier onset of spring each year. This decline could be causing a “mismatch” between animals with white coats and the snowless ground, explains lead author Prof Scott Mills, vice president of research for global change and sustainability at the University of Montana. He tells Carbon Brief:

“All of these species literally live or die by the effectiveness of their camouflage, which evolution has exquisitely crafted to match the average duration of winter snow.”

This mismatch could make some animals, such as hares, more vulnerable to predators, he says. It could also make it harder for predators, such as the arctic fox, to effectively hunt their prey. Mills says:

“One thing to realise is that all 21 of these species, including the carnivores, are prey: Arctic fox get clobbered by golden eagles, weasels are killed by foxes, coyotes, and raptors. For the hares and rodents, tasty snacks for multiple predators, camouflage is everything.”

Arctic fox (Alopex lagopus) in snow, Churchill, Manitoba, Canada, North America. Credit: robertharding / Alamy Stock Photo

Charting colour change

For the study, the researchers first collected coat colour and location data for more than 2,500 live animals and museum specimens spanning 60 countries.

They then analysed this data using modelling to study the moulting behaviour of animals living in different parts of the world.

The researchers found that, within one species, not all individuals will moult in the winter.

The chances of an animal moulting depend on the landscape in which they live. The more snowy the landscape, the higher the chance an animal will turn white in the winter.

This is shown on the chart below, where the number of snow-covered days per year is plotted against the likelihood of turning white in the winter for the Japanese hare (dark blue), the white-tailed jackrabbit (light blue), the least weasel (yellow) and the long-tailed weasel (red).

The probability of a colour-changing mammal having a white winter coat in regions with 0-320 days of snowfall per year. Results are shown for the Japanese hare (dark blue), the white-tailed jackrabbit (light blue), the least weasel (yellow) and the long-tailed weasel (red). Source: Mills et al. (2018)

The chart also includes a “broad polymorphic zone”. A “polymorphic zone” is a term used to describe regions where the probability of having either a brown or white winter coat is close to equal.

In these “zones”, mammals could have the best chance of adapting to declining snowfall conditions, Mills says. That is because, in these areas, a proportion of each species do not turn white in the winter and are therefore more able to blend in with snowless environments.

These brown-coated animals will be more likely to survive winters with less snow cover and pass on their genes to their offspring. Over time, this would increase the proportion of animals with brown winter coats, allowing the population to adapt – and ultimately survive – in environments with less snow.

The maps below show where the polymorphic zone of two or more species overlap. On the charts, red shows where the zones of two species overlap, while brown shows areas where the zones of three species overlap.

Regions in North America (A) and Eurasia (B) with polymorphic zones in winter coat colour for more than two species (red) and more than three species (brown). Source: Mills et al. (2018)

The charts show that parts of the US, Canada and Scotland show the largest overlap.

These regions could be considered “evolutionary rescue zones” where a number of colour-changing mammal species could be able to adapt to declining snowfall, says Mills:

“Because areas with the most [coat colour] variation evolve most quickly, these ‘polymorphic’ zones emerge as hotspots for rapid evolutionary response to climate change. Here in the polymorphic zones the populations are most likely to rapidly evolve towards winter brown, and to disperse the winter brown genes out into the adjacent winter white populations.”

The species whose range most commonly fall into these zones include the arctic fox, the white-tailed jackrabbit and the long-tailed weasel, the research finds. These species may have the best chance of adapting to declining winter snowfall, Mills says, but it is still too soon to tell what their chances of survival could be:

“To really evaluate risk to various species will require a lot more fieldwork and genetic analyses for other species, like we’ve been doing with snowshoe hares. We’re starting to work with weasels and Arctic fox, but I really hope that this paper initiates researchers around the world to start investigating coat colour mismatch.”

Picture of change

The findings should provide “yet another push to policymakers” to reduce the “global carbon footprint”, Mills says:

“I hope that the picture of white animals on brown snowless ground ‘paints a thousand words’ that shows that with continued human-caused climate change and reduction in snow duration, winter white animals on a brown snowless winter background will be in trouble.”

The research also shows that conserving “evolutionary rescue zones” could help wildlife to survive future climate change, Mills says:

“I hope it also helps [policymakers] see that other short-term, yet effective, options are available for protecting wildlife in the face of climate change.”

The post Animals with white winter camouflage could struggle to adapt to climate change appeared first on Carbon Brief.

Carbon emissions from Amazon wildfires could ‘counteract’ deforestation decline

The loss of carbon from wildfires fuelled by drought could “counteract” efforts to cut deforestation in the Amazon rainforest, research suggests.

A new study finds that, while rates of deforestation have sharply fallen in the Amazon over the past decade, the number of wildfires affecting the region has remained stubbornly high – particularly in drought years.

Emissions from wildfires totalled more than 1bn tonnes of CO2 from 2003-2015, the lead author tells Carbon Brief, and climate change, along with forest fragmentation, could cause a further increase in the number of forest fires in the coming decades.

The author adds that, if current efforts to curb deforestation are reversed, the combination of forest fires and deforestation could cause carbon loss from the Amazon to “escalate to proportions never experienced before”.

Three billion trees

The Amazon rainforest is the largest rainforest in the world, spanning an area that is 25 times the size of the UK.

The forest’s three billion trees absorb CO2 from the atmosphere during photosynthesis and then use it to build new leaves, shoots and roots. As they grow, these trees account for a quarter of the CO2 absorbed by the land each year.

The new study, published in Nature Communications, explores how this enormous carbon store is being affected by both deforestation and drought-driven wildfires.

The clearing of trees during deforestation causes previously locked-up carbon to be released back into the atmosphere.

The study finds that, despite remaining a major driver of forest carbon loss, rates of deforestation in the Amazon have fallen by 76% between 2003 and 2015. This reflects efforts by the Brazilian government to curb both legal and illegal deforestation, the study notes.

However, the amount of carbon loss from drought-driven wildfires has remained high, says lead author Dr Luiz Aragão, leader of the tropical ecosystems and environmental sciences group (TREES) at the National Institute for Space Research in Brazil. He tells Carbon Brief:

“This is the first time that we could clearly demonstrate how much widely-spread forest fires during recent droughts influence Amazonian carbon emissions. During these droughts, forest fires can overtake emissions from deforestation.”

Fanning the flames

Glossary

El Niño: Every five years or so, a change in the winds causes a shift to warmer than normal sea surface temperatures in the equatorial Pacific Ocean – known as El Niño. Together with its cooler counterpart, La Niña, this is known as the El Niño Southern Oscillation (ENSO) and is responsible for most of the fluctuations in temperature and rainfall patterns we see from one year to the next.

El Niño: Every five years or so, a change in the winds causes a shift to warmer than normal sea surface temperatures in the equatorial Pacific Ocean – known as El Niño. Together with… Read More

Although wildfires occur regularly in the Amazon, fire incidence is at its highest in drought years.

“Drought years” happen on average every five years in the Amazon and are typically a result of changes to wind and weather patterns brought about by warming in the Atlantic Ocean during events of the climate phenomenon El Niño.

Although droughts have been a natural part of the year-to-year variations in the Amazon’s climate, both the frequency and severity of droughts in the rainforest have been increasing over the last decade because of climate change, Aragão says:

“These natural swings can be intensified by global warming. Another catalyst of this Atlantic oceanic warming is the declining Northern Hemisphere aerosol production, which is also influenced by climate change.”

Previous research (pdf) shows that aerosols influence cloud formation in the rainforest and, therefore, the amount of regional rainfall.

Wildfires are usually sparked by humans clearing land, either for small-scale farming or major deforestation, Aragão says. During drought years, these small fires can quickly spread to large areas of the rainforest.

A lack of rainfall during drought years causes large sections of the lush canopy to dry out and die. These dry, dead leaves can then act as tinder, allowing small fires to spread, says Aragão:

“These forests would not burn naturally. Most of the fires that happen during droughts are human-driven. When the climate is drier, fires that are set for land management are more likely to leak into surrounding forests.”

As large areas of forest burn, huge stores of previously stored carbon are released into the atmosphere. The amount of carbon loss is greatest when fires “leak into” previously pristine forest, which may have been storing carbon for decades or even centuries, Aragão adds.

Assessing the damage

The researchers used satellite data to record the number and regional spread wildfires in the Amazon from 2003-15. The figure below shows the annual fire counts of each year of the study (red bars and numbers), with bold text signifying drought years (2005, 2010 and 2015). The numbers on the x-axis correspond to the fire season months from June (month 6) to December (month 12).

The length of the grey bars corresponds to the sum of all months with more than 10,000 fires. The colour within the grey bar shows the number of fire counts during the year’s “peak month”, with dark red showing a count of more than 40,000 and green showing a count of 10,000 to 15,000.

The chart also displays annual deforestation rates in the Amazon (khaki bars), which were derived from the Brazilian government.

The chart shows how the number of forest fires tends to spike in drought years. For example, during the 2015 drought, fire incidence was 36% higher compared to the average for the previous 12 years, the study finds.

Annual absolute fire counts (red bars) and deforestation rates (khaki bars) in the Amazon from 2003-15. Number of fires during drought years (2005, 2010, 2015) are shown in bold. The length of the grey bars corresponds to the sum of all months with more than 10,000 fires. The colour within the grey bar shows the number of fire counts during the year’s “peak month”, with dark red showing a count of more than 40,000 and green showing a count of 10,000 to 15,000. Source: Aragão (2018)

The results show that, while deforestation rates are decreasing, forest fire counts have not seen a similar decline.

This suggests that the role that deforestation plays in sparking forest fires is diminishing over time, says Aragão:

“Before we used to observe that fires in Amazonia were strongly related to deforestation. Now this relationship is weak. We think that there are few explanations, but a strong one is that because the Amazon is more fragmented, there are more edges between the deforested land and forests. This increases the chances of fires from open lands to propagate into forests.”

The effect of fragmentation could be magnified by future climate change, which is expected to bring more extreme droughts to the Amazon, he says:

“We expect that drought intensity and frequency will increase towards the end of the century. So, with more droughts it is very likely that fire incidence will also increase if no policy actions are taken to curb ignition sources.”

The researchers also used satellite data to record the total amount of CO2 released as a result of deforestation and wildfires over the study period.

The results are shown on the chart below, which shows annual CO2 emissions in teragrams (one teragram is equal to 1m tonnes of CO2) for forest fires (dark green) and deforestation (light green).

Over the course of the study period, emissions from wildfires in drought years alone totalled more than 1bn tonnes, Aragão says. The release of CO2 during forest fires could increase further as the climate warms, he adds.

Annual CO2 emissions in teragrams (1m tonnes) of forest fires (dark green) and deforestation (light green) in the Amazon from 2003 to 2015. Source: Aragão (2018)

‘Compelling’ results

The “comprehensive” study raises concerns over the growing threat of wildfires in the Amazon, says Prof Guido van der Werf from Vrije University in the Netherlands, who was not involved in the study. Van der Werf was part of a team that developed the Global Fire Emissions Database. He tells Carbon Brief:

“What is particularly compelling to me is the observed decoupling of fire and deforestation; they used to go hand in hand as fire was the cheapest tool in the deforestation process, but in recent years fires are observed more outside the deforestation regions, especially during drought years.

“Controlling these forest fires may be more difficult than controlling deforestation as it only takes one simple ignition to burn down a large area and many fires occur in secondary forests which may be less well monitored.”

The research uses a “sound methodology” but relies on statistics from the Brazilian government, which research suggests could be overstating recent deforestation reductions, says Dr Richard Birdsey, a senior scientist specialising in quantifying forest carbon budgets from the Woods Hole Research Centre, who also wasn’t involved in the research. He tells Carbon Brief:

“Some studies question the official statistics of deforestation in Brazil, suggesting that the reduction over previous decades may be overestimated. If deforestation is higher than the estimate used in this paper, then the relative effect of drought-induced fire would not be as large as stated here, and the decoupling of fire incidence from deforestation rates would not be as significant.”

Another factor not considered in the study is that forests tend to recover more quickly from wildfires than deforestation, he adds:

“Fires create young forests that will rather quickly recover significant amounts of lost biomass and usually have higher productivity compared with old-growth for several decades. Thus, considering the effects of fires over decades is an important consideration not addressed in this paper.”

Further carbon loss as a result of drought-driven wildfires could “counteract” efforts to curb deforestation in the Amazon, says Aragão. And, if efforts to stop deforestation are unsuccessful, the scale of carbon loss from the Amazon could reach “unprecedented” levels, he says:

“The main worry is that if deforestation increases, in combination with the increase fragmentation, increase in drought probability [caused by climate change] and the use of fires by humans, carbon emissions could escalate to proportions never experienced before.”

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Volvo Ocean Race Research Finds Microplastics In Remote Regions

Samples taken from the most remote parts of the ocean by the contestants in the Volvo Ocean Race has found surprisingly high concentrations of microplastics in an area where there is virtually no human activity.

Acidification could leave oceans ‘uninhabitable’ for cold-water corals

The world’s oceans could become “uninhabitable” for cold-water corals by the end of the century as a result of ocean acidification, research suggests.

Ocean acidification, which occurs as seawater takes up CO2 from the atmosphere, could threaten around 70% of cold-water coral living below 1,500 metres in the North Atlantic Ocean by 2050, the research finds.

Acidified waters that accumulate in the North Atlantic could then be circulated to the global seas via a system of ocean currents, the lead author tells Carbon Brief, which could have consequences for reefs across the world.

The findings reiterate how many coral reefs could “dissolve” and “crumble” as the world continues to warm, another scientist tells Carbon Brief.

Cool corals

Cold-water corals make up more than half of known coral species in the world. They are found in deep, dark parts of the world’s oceans in both the northern and southern hemisphere. They can thrive at depths of up to 2,000 metres and in water temperatures as low as 4C.

Unlike tropical corals, cold-water corals do not rely on colourful algae for their food. Instead, cold-water coral feed on floating plankton.

This means they are unaffected by coral bleaching, a process which is heightened by climate change and poses a great threat to the survival of tropical reefs, such as the Great Barrier Reef.

However, both tropical and cold-water coral species are threatened by a process known as “ocean acidification”, which occurs as seawater absorbs CO2 from the atmosphere.

The oceans have absorbed around 30% (pdf) of the CO2 released by human activity since the industrial revolution. This has caused oceans, which are alkaline, to become more acidic over time. The overall pH of seawater has fallen from around 8.2 to 8.1 from pre-industrial times to the present day.

This change has altered the levels of a type of calcium carbonate known as aragonite in seawater. Some types of coral, known as “hard coral”, have tough outer skeletons that are made out of this substance.

In seawater, there is a boundary known as the “aragonite saturation horizon” (ASH). Above the boundary, seawater is saturated with aragonite, which provides preferable conditions for the corals. However, below the boundary, seawater is undersaturated with aragonite. These waters are corrosive to hard corals and, over time, can cause their skeletons to dissolve.

The new research, published in Nature, investigates how ocean acidification has caused the height of this boundary to change over time.

Blotched Hawkfish (Cirrhitichthys aprinus), Mie, Japan, 2016. Credit: Noriyuki Otani / Alamy Stock Photo.

Crossing the line

Using observational data taken between 2002 and 2016, the researchers find that cold-water corals tend to live in parts of the world where the ASH is still relatively deep, explains Dr Fiz Perez, a researcher at the Marine Research Institute in Vigo, Spain. He tells Carbon Brief:

“We establish a link between the global distribution of cold-water corals and aragonite saturation horizon. In the North Atlantic, the ASH is deep enough and reefs are large; in contrast, in the Pacific, the ASH is shallower and reefs are patchy.”

This is shown on the map below. The turquoise shading shows where the ASH tends to be relatively deep (1,500-2,000 metres), while the dark blue shows where the ASH occurs at relatively shallow depths.

On the map, circles, diamonds and squares represent the locations of cold-water coral reefs, with white showing reefs living at relatively shallow depths and black showing reefs living at depths below 1,000 metres.

Global aragonite saturation and cold-water coral distribution. Turquoise indicates a relatively deep saturation boundary while dark blue shows a relatively shallow saturation boundary. Circles, diamonds and squares represent the locations of cold-water coral reefs, with white showing reefs living at relatively shallow depths and black showing reefs living at depths below 1,000m. Source: Perez et al. (2018)

However, even in the North Atlantic, the ASH is rapidly rising, the researchers find. In the Irminger Sea off the southern coast of Iceland, for example, the boundary has risen by 10-15 metres per year between 2002 and 2016.

As the boundary rises, the proportion of cold-water corals exposed to corrosive seawater also increases, Perez says. This is likely to continue under future CO2 emissions, the study finds.

Using statistical modelling, the researchers show that, in a future scenario – where the concentration of human-released CO2 in the atmosphere doubles within three decades – cold-water corals could be “severely” threatened. Perez says:

“With the current progression of carbon emissions, around 70% of North Atlantic cold-water corals will be affected by ocean acidification by 2050-60. Obviously, the proportion will be larger in the 2100, but it would depend on the pathway of future greenhouse gas emissions.”

Global conveyor belt

The researchers also investigated how corrosive waters that build up in the North Atlantic could spread to other parts of the world via a system of ocean currents known as the Atlantic Meridional Overturning Circulation (AMOC).

This “global ocean conveyor belt” brings water from the North Atlantic northward towards to poles, before returning southward towards the equator at much deeper depths.

The research suggests that AMOC is transporting acidified seawater – which is undersaturated in aragonite – to the deep ocean, where it exposes deep-sea corals to corrosion. The transport of aragonite towards the deep ocean has dropped by 44% since the industrial revolution, the study finds.

Under their future scenario, the researchers project that the transport of aragonite could fall by as much as 79% compared to pre-industrial levels, which may “severely endanger cold-water coral habitats”. The global ocean conveyor could then “export this acidified deep water southwards, spreading corrosive waters to the world ocean,” the study warns.

‘Ecosystem engineers’

The impact of ocean acidification on cold-water coral reefs could have far-reaching consequences for marine wildlife, Perez says.

This is because cold-water reefs are “ecosystem engineers”, providing a place for fish and shellfish to meet and breed in an otherwise barren landscape, he says:

“The important point is that a whole ecosystem is developed in the surroundings of the cold-water coral reefs.”

The reefs are also the breeding and spawning grounds of a number of economically-important fish, including Pacific cod, Pacific halibut and Atka mackerel.

Although scientists are still unsure as to how exposure to corrosive waters could affect the survival rate of cold-water coral, the findings indicate that many reefs are likely to “crumble” as the climate warms, says Prof Jean-Pierre Gattuso from the Institute for Sustainable Development and International Relations (IDDRI), who was not involved in the research. He tells Carbon Brief:

“The jury is still out on the direct effect of such corrosive waters on [live] deep-sea corals, but there is little doubt that dead coral skeletons will dissolve. As a result, there is little doubt that the 3D structures harbouring of these highly diverse communities will progressively crumble.”

The findings show that climate change could make the ocean “uninhabitable” for cold-water coral by the end of the century, Perez says:

“If we continue the path of a ‘business as usual’ development, based on fossil fuel burning, the ocean will become uninhabitable for cold-water corals. Even if the humankind were able to keep below 2C of warming, many deep cold-water corals would be affected.”

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