Hurricane Matthew was a powerful and devastating tropical cyclone which became the first Category 5 Atlantic hurricane since Hurricane Felix in 2007. The thirteenth named storm, fifth hurricane and second Read More ... major hurricane of the above-average 2016 Atlantic hurricane season, Matthew wrought widespread destruction and catastrophic loss of life during its journey across the Western Atlantic, including parts of Haiti, Cuba, Dominican Republic, the Lucayan Archipelago, the southeastern United States, and the Canadian Maritimes. A total of 603 deaths have been attributed to the storm, including 546 in Haiti, 47 in the United States, 4 in Cuba, 4 in the Dominican Republic, 1 in Colombia, and 1 in Saint Vincent and the Grenadines, making it the deadliest Atlantic hurricane since Hurricane Stan in 2005, which killed 1,600 in Central Mexico. With the storm causing damages estimated in excess of US$15 billion, it was also the most destructive Atlantic hurricane since Hurricane Sandy in 2012, as well as the ninth-costliest Atlantic hurricane in recorded history.
Originating from a tropical wave that emerged off Africa on September 22, Matthew developed into a tropical storm just east of the Lesser Antilles on September 28. It became a hurricane north of Venezuela and Colombia on September 29, before undergoing explosive intensification, ultimately reaching Category 5 intensity on October 1 at just 13.4°N latitude – the lowest latitude ever recorded for a storm of this intensity in the Atlantic basin, breaking a record set by Hurricane Ivan in 2004. Matthew weakened slightly and fluctuated in intensity while making a northward turn toward the Greater Antilles, remaining a strong Category 4 hurricane as it made its first landfall over Haiti's Tiburon Peninsula early on October 4, and then a second one in Cuba later that day. Matthew weakened somewhat but re-intensified as it tracked northwest, making landfall in the northern Bahamas. The storm then paralleled the coast of the southeastern United States over the next 36 hours, gradually weakening while remaining just offshore before making its fourth and final landfall over the Cape Romain National Wildlife Refuge near Myrtle Beach, South Carolina as a Category 1 hurricane on the morning of October 8. Matthew re-emerged into the Atlantic shortly afterward, eventually completing its transition into an extratropical cyclone as it turned away from Cape Hatteras, North Carolina on October 9.
Widespread effects were felt from Matthew across its destructive path, however, the most significant impacts were felt in Haiti, with US$1.9 billion in damage and 546 deaths. The combination of flooding and high winds disrupted telecommunications and destroyed extensive swaths of land; around 80% of Jérémie sustained significant damage. Four people were killed in Cuba due to a bridge collapse, and total losses in the country amounted to US$2.58 billion, most of which occurred in the Guantánamo Province. Passing through the Bahamas as a major hurricane, Matthew spread damage across several islands, compounding relief efforts from Hurricane Joaquin which had pounded similar areas just the previous year. Grand Bahama was hit directly, where most homes sustained damage in the townships of Eight Mile Rock and Holmes Rock. Preparations began in earnest across the southeastern United States as Matthew approached, with several states declaring states of emergencies for either entire states or coastal counties; widespread evacuations were ordered for extensive areas of the coast because of predicted high wind speeds and flooding, especially in the Jacksonville Metropolitan Area. In Florida, over 1 million lost power as the storm passed to the east, with 478,000 losing power in Georgia and South Carolina. While damage was primarily confined to the coast in the Florida and Georgia, torrential rains spread inland in the Carolinas and Virginia, causing widespread flooding
How humans populated the globe
1# Genetic studies offer new insights into the ancient exodus out of Africa
No paper or digital trails document ancient humans’ journey out of Africa to points around the globe. Fortunately, those intrepid travelers left a DNA trail. Genetic studies released in 2016 put a new molecular spin on humans’ long-ago migrations. These investigations also underscore the long trek ahead for scientists trying to reconstruct Stone Age road trips.
“I’m beginning to suspect that the ancient out-of-Africa process was complex, involving several migrations and subsequent extinctions,” Read More ... says evolutionary geneticist Carles Lalueza-Fox of the Institute of Evolutionary Biology in Barcelona.
Untangling those comings, goings and dead ends increasingly looks like a collaborative job for related lines of evolutionary research — comparisons of DNA differences across populations of present-day people, DNA samples retrieved from the bones of ancient hominids, archaeological evidence, fossil finds and studies of ancient climates. It’s still hard to say when the clouds will part and a clear picture of humankind’s journey out of Africa will appear. Consider four papers published in October that featured intriguing and sometimes contradictory results.
Three new studies expanded the list of present-day populations whose DNA has been analyzed. The results suggest that most non-Africans have inherited genes from people who left Africa in a single pulse between about 75,000 and 50,000 years ago (SN: 10/15/16, p. 6). One team, studying DNA from 142 distinct human populations, proposed that African migrants interbred with Neandertals in the Middle East before splitting into groups that headed into Europe or Asia. Other scientists whose dataset included 148 populations concluded that a big move out of Africa during that time period erased most genetic traces of a smaller exodus around 120,000 years ago. A third paper found that aboriginal Australians and New Guinea’s native Papuans descend from a distinctive mix of Eurasian populations that, like ancestors of other living non-Africans, trace back to Africans who left their homeland around 72,000 years ago.
The timing of those migrations may be off, however. A fourth study, based on climate and sea level data, identified the period from 72,000 to 60,000 years ago as a time when deserts largely blocked travel out of Africa. Computer models suggested several favorable periods for intercontinental travel, including one starting around 59,000 years ago. But archaeological finds suggest that humans had already spread across Asia by that time.
Clashing estimates of when ancient people left Africa should come as no surprise. To gauge the timing of these migrations, scientists have to choose a rate at which changes in DNA accumulate over time. Evolutionary geneticist Swapan Mallick of Harvard Medical School and the other authors of one of the new genetics papers say that the actual mutation rate could be 30 percent higher or lower than the mutation rate they used. Undetermined levels of interbreeding with now-extinct hominid species other than Neandertals may also complicate efforts to retrace humankind’s genetic history (SN: 10/15/16, p. 22), as would mating between Africans and populations that made return trips.
“This can be clarified, to some extent, with genetic data from ancient people involved in out-of-Africa migrations,” says Lalueza-Fox. So far, though, no such data exist.
The uncertainty highlights the need for more archaeological evidence. Though sites exist in Africa and Europe dating from more than 100,000 years ago to 10,000 years ago, little is known about human excursions into the Arabian Peninsula and the rest of Asia. Uncovering more bones, tools and cultural objects will help fill in the picture of how humans traveled, and what key evolutionary transitions occurred along the way.
Mallick’s team has suggested, for example, that symbolic and ritual behavior mushroomed around 50,000 years ago, in the later part of the Stone Age, due to cultural changes rather than genetic changes. Some archaeologists have proposed that genetic changes must have enabled the flourishing of personal ornaments and artifacts that might have been used in rituals. But comparisons of present-day human DNA to that of Neandertals and extinct Asian hominids called Denisovans don’t support that idea. Instead, another camp argues, humans may have been capable of these behaviors some 200,000 years ago.
Nicholas Conard, an archaeologist at the University of Tübingen in Germany, approaches the findings cautiously. “I do not assume that interpretations of the genetic data are right,” he says. Such reconstructions have been revised and corrected many times over the last couple of decades, which is how “a healthy scientific field moves forward,” Conard adds. Collaborations connecting DNA findings to archaeological discoveries are most likely to produce unexpected insights into where we come from and who we are.
Sea ice loss will shake up ecosystems
1# Polar bears aren’t the only organisms affected by Arctic melting
In a better world, it would be the big news of the year just to report that Arctic sea ice shrank to 4.14 million square kilometers this summer, well below the 1981–2010 average of 6.22 million square kilometers (SN Online: 9/19/16). But in this world of changing climate, extreme summer ice loss has become almost expected. More novel in 2016 were glimpses of the complex biological consequences of melting at the poles and the opening of Arctic passageways, talked about for at least a decade and now Read More ... well under way.
With top-of-the-world trade and tourist shortcuts opening, less ice means more travel. Europe-to-Asia shipping routes will typically shorten by about 10 days by midcentury, a report in Geophysical Research Letters predicted. Hopes for Northwest Passage routes obsessed (and killed) explorers in previous centuries, but in 2016, the thousand-passenger cruise ship Crystal Serenity offered the first megascale tourist trip from Alaska to New York with fine dining, casino gambling and an escort icebreaker vessel.
Biologists are delving into consequences for organisms other than human tourists — or the much-discussed polar bear. “There’s been a marked shift in the research community,” says climate change ecologist Eric Post of the University of California, Davis. There’s new interest in considering more than just species that dwell on sea ice, with researchers looking for the less direct effects of declining ice.
In the February Global Change Biology, eight scientists issued a call for observations of what could be early signs of faunal exchange: the mingling of Atlantic and Pacific species. One possible indicator is the sighting of gray whales off the coast of Namibia and also off Israel, even though that species went extinct in the Atlantic two centuries ago. These whales feed by snouting around in soft ocean bottoms, adding another predator to the system but also creating new habitat opportunities for some creatures (SN: 1/23/16, p. 14).
Since the call was published, biodiversity scientist Seabird McKeon of Colby College in Waterville, Maine, has heard new reports, such as a sighting of an ancient murrelet off the coast of Maine. It’s not the first wrong-coast report for the bird, which typically resides in the northern Pacific, but repeat sightings could be important, too. “What I think we’re seeing is not just new species coming across, but also perhaps an increased chance of survival and reproduction if more come over,” McKeon says. He is hoping to get new data from the online Encyclopedia of Life’s upcoming Fresh Data system, which connects scientists to people reporting nature observations.
PLANT PROBLEMS The melting of Arctic ice could affect seed dispersal among plants, such as the dwarf birch (shown here in Greenland).
KIM HANSEN/WIKIMEDIA COMMONS (CC BY SA-2.5)
For terrestrial northerners, melting ice often means loss of mobility. Peary caribou on the 36,000 or more islands of Canada’s northern archipelago occasionally use ice bridges to travel to new territories and mix genes with other populations. Yet ice losses since 1979 have made it some 15 percent harder to find traveling paths, researchers reported in September in Biology Letters (SN: 10/29/16, p. 8).
Even some plants such as dwarf birch probably travel by ice, scientists also reported in September in Biology Letters. Reconstructing long-ago sea ice extent and plant colonization dates suggests that seeds hitchhiked on slowly creeping frozen conveyors around northern Europe to colonize new territory at the end of the Ice Age. Losing ice roads could lead to tattered, disconnected populations as recolonization becomes less likely. Yet, there are pluses and minuses, says Post, who is helping to develop a package of scientific articles for Biology Letters on the biological effects of sea ice loss. Reseeding populations after a wipeout could be more difficult with tattered ice, but for the highly specialized and vulnerable plants very far north, the loss of sea ice could slow the arrival of invasive species that threaten the natives.
The minimum summer sea ice extent since 1979 has declined by about 87,000 square kilometers per year, equivalent to an area more than three times the size of New Jersey disappearing annually, as Post has put it. The September 2016 sea ice minimum didn’t break a record, as some had expected it might. It tied for second worst, behind the 2012 minimum, and roughly equaled the 2007 minimum. 2016 did set a new record low for winter Arctic ice extent (SN Online: 3/28/16).
Sea ice changes reverberate through the ecosystem. Ice melting cues the springtime phytoplankton blooms that feed copepods and other tiny marine grazers. The grazers feed their predators and, in turn, the predators of those predators. In years when spring warming brings an early ice retreat, the phyto-plankton bloom is not a huge, rich burst. It favors smaller grazing zooplankton that don’t fuel as much of a boom in their predators, marine ecologist Martin Renner of Homer, Alaska, and colleagues reported in a paper for the Biology Letters special collection.
Tracing the effects of shrinking ice through these grazers to fish to seabirds revealed a tangled web of ups and downs and shifting foraging grounds. In the end, Renner and colleagues predict “a very different eastern Bering Sea ecosystem and fishery than we know today.” And that may be far from the only sea change in the far north.