Coral reefs are classified by estimated present threat from local human activities, according to the Reefs at Risk Revisited integrated local threat index.The index combines the threat from the following activities: overfishing and destructive fishing, coastal development, watershed-based pollution, and marine-based pollution and damage.
A major new survey of the world's coral reefs finds that they are in trouble. Big trouble.
Overfishing and local pollution continue to grow as threats, and the reefs' long-term existence is in doubt because the world's oceans are gradually getting warmer and more acidic because of human activity.
There's a lot at stake: Coral reefs are spectacular ecosystems, overflowing with diverse and colorful marine life.
They're also the source of food and economic sustenance to half a billion people around the world.
"Currently, we find 75 percent of the world's reefs are threatened by a combination of local and global threats," says Lauretta Burke, a senior author of the new report.
"By 2030, the percentage will rise to 90 percent. By 2050, virtually all reefs will be threatened," she says.
Many of the risks are familiar and long-standing.
At a news conference Wednesday, Lauretta Burke, of the World Resources Institute, talked about overfishing, and runoff of sewage and sediments from the shore.
"But perhaps the most shortsighted threat to reefs is the use of destructive fishing practices: the use of poisons to stun and capture fish, the use of explosives to kill fish," she says.
Abundant sea life with hard and soft corals grows on a coral reef in the Indonesia-Pacific region.
The report also folds in global threats.
Greenhouse gases pouring into the atmosphere from our tailpipes and chimneys warm the oceans, causing heat stress to corals.
Lots of that carbon dioxide also dissolves in the ocean, creating carbonic acid, which can eventually corrode coral and other shell-building animals.
Add it all together, and one-third of all coral species are at risk of extinction, says Nancy Knowlton of the Smithsonian Institution's Marine Biology Research Institution.
"This makes corals the most endangered animal on the planet," she says, "even more endangered than frogs, which have gotten a lot of press because of the diseases that have wiped out a lot of frog populations. And of course this is just the corals — it doesn't count all the things that depend on corals."
Dealing with the threats
"These are dire projections," Burke says.
But it doesn't have to be that way: "These results assume no improvement in management, no reduction in local threats, and that we continue on our current trajectory of greenhouse gas emissions."
And that current emissions trajectory gives us a small grace period.
"The tipping point comes sometime between 2040 and 2050, which is not that far away," Knowlton says.
Local threats are potentially easier to deal with, and there has been some progress in that regard.
For example, President George W. Bush created vast marine protected areas in the Pacific to preserve reefs in U.S. territorial waters.
"We obviously need more marine protected areas," Knowlton says.
"Not just big ones like these, but small ones, local ones in the developing world, where major marine protected areas aren't financially possible, but small protected areas can do a lot of good."
In releasing this report today, the World Resources Institute got help from one of the premiere marine biologists in this country — Jane Lubchenco, who now runs the U.S. National Oceanic and Atmospheric Administration.
"It will take a Herculean effort to reverse the current trajectory and leave healthy ocean ecosystems to our children and our grandchildren," she said.
And nobody sounded too optimistic about that task.
Links :
- WRI : Reefs at risk revisited: threats and response
- TheGuardian : Coral reefs report warns of mass loss threat
- BBCNews : Coral reefs heading for fishing and climate crisis
- EnvironmentNewsService : Warming, polluted oceans imperil 75 percent of all coral reefs
- Treehugger : New method for predicting extinctions could help save coral reefs
- Care2 : 75% of Earth’s coral reefs threatened
From DiscoverMagazine
In 1996, a loggerhead turtle called Adelita swam across 9,000 miles from Mexico to Japan, crossing the entire Pacific on her way.
Wallace J. Nichols tracked this epic journey with a satellite tag.
But Adelita herself had no such technology at her disposal.
How did she steer a route across two oceans to find her destination?
Nathan Putman has the answer.
By testing hatchling turtles in a special tank, he has found that they can use the Earth’s magnetic field as their own Global Positioning System (GPS).
By sensing the field, they can work out both their latitude and longitude and head in the right direction.
Putman works in the lab of Ken Lohmann, who has been studying the magnetic abilities of loggerheads for over 20 years.
In his lab at the University of North Carolina, he places hatchlings in a large water tank surrounded by a large grid of electromagnetic coils.
In 1991, he found that the babies started swimming in the opposite direction if he used the coils to reverse the direction of the magnetic field around them.
They could use the field as a compass to get their bearing.
Later, Lohmann showed that they can also use the magnetic field to work out their position. For them, this is literally a matter of life or death.
Hatchlings born off the coast of Florida spend their early lives in the North Atlantic gyre, a warm current that circles between North America and Africa.
If they’re swept towards the cold waters outside the gyre, they die. Their magnetic sense keeps them safe.
Using his coil-surrounded tank, Lohmann could mimic the magnetic field at different parts of the Earth’s surface.
If he simulated the field at the northern edge of the gyre, the hatchlings swam southwards.
If he simulated the field at the gyre’s southern edge, the turtles swam west-northwest.
These experiments showed that the turtles can use their magnetic sense to work out their latitude – their position on a north-south axis.
Now, Putman has shown that they can also determine their longitude – their position on an east-west axis.
He tweaked his magnetic tanks to simulate the fields in two positions with the same latitude at opposite ends of the Atlantic.
If the field simulated the west Atlantic near Puerto Rico, the turtles swam northeast.
If the field matched that on the east Atlantic near the Cape Verde Islands, the turtles swam southwest.
In the wild, both headings would keep them within the safe, warm embrace of the North Atlantic gyre.
Before now, we knew that that several animal migrants, from loggerheads to reed warblers to sparrows had some way of working out longitude, but no one knew how.
By keeping the turtles in the same conditions, with only the magnetic fields around them changing, Putman clearly showed that they can use these fields to find their way.
In the wild, they might well also use other landmarks like the position of the sea, sun and stars.
Human sailors also worked out how to measure longitude, as described in Dava Sobel’s bestselling book.
They relied on an accurate clock created by the Englishman John Harrison, which allowed them to compare the time of day at a given location with that at a distant place.
Every hour of difference represented fifteen degrees of longitude.
But we know that turtles don’t use a similar time-based method because Putman didn’t test them under different conditions of light or dark.
His hatchlings had no way of telling what time it was. Indeed, to use a time-based map in the wild, the turtles would need to have an internal clock that stayed set at Florida time for their entire 3-15 year migration.
Instead, Putman thinks that the turtles work out their position using two features of the Earth’s magnetic field that change over its surface.
They can sense the field’s inclination, or the angle at which it dips towards the surface.
At the poles, this angle is roughly 90 degrees and at the equator, it’s roughly zero degrees.
They can also sense its intensity, which is strongest near the poles and weakest near the Equator.
Different parts of the world have unique combinations of these two variables.
Neither corresponds directly to either latitude or longitude, but together, they provide a “magnetic signature” that tells the turtle where it is.
Scientists often talk about a magnetic “map”, but the animals aren’t necessarily using any sort of mental chart.
As with all research in magnetic senses, it’s very hard to work out what the animal is actually sensing or thinking.
But that can be a bonus.
“It might be good because I don’t have any preconceived notions about how animals like turtles use magnetic information,” says Putman.” I can let the turtles tell me what they can respond to without imposing any personal expectations on them!”
We do, however, know that they have their super-sense from birth.
Putman’s turtles had never been in the ocean before and their magnetic sense doesn’t depend on experience.
Indeed, Lohmann’s previous experiments showed that even newly hatched loggerheads can react correctly to different magnetic fields.
These studies weren’t easy. Putman says,
“The loggerheads we use are a threatened species, so we have to be extra careful with all of them. We use newly hatched turtles for these studies, so we work with them and release them at night. We try to design really short experiments and house them for no more than a couple of hours before letting them go. [It] makes for rushed data collection!”
For Lohmann, these tribulations are worth it.
After spending graduate school on spiny lobsters and sea slugs (two animals that also have magnetic senses), he had an opportunity to study young loggerheads.
“I thought it was worth a try to see if turtles could detect magnetic fields. I figured that after the two-year project was over, I would get back to the invertebrates,” says Lohmann.
“That was 23 years ago, and I’m still studying turtles. Each time we think we have it all figured out, the turtles show us that we have missed something important.”
Links :
- BBCNews : Sea turtles' migration mystery is 'solved'
- Wired : Navigational 'Magic' of sea turtles explained
8 charts have been updated in the Marine GeoGarage (Linz january update published February, 2011) :
- NZ48 : Western Approaches to Cook Strait
- NZ61 : Karamea River to Stephens Island
- NZ443 : Approaches to Port Taranaki
- NZ614 : Tasman Bay
- NZ5223 : Great Barrier Island (Northwestern Part)
- NZ5224 : Great Barrier Island (Southern Part)
- NZ5324 : Tamaki Strait and Approaches including Waiheke Island
- NZ5325 : Tamaki River
Today 178 charts / 340 including sub-charts for New Zealand are displayed in the Marine GeoGarage.
Note : LINZ produces official nautical charts to aid safe navigation in New Zealand waters and certain areas of Antarctica and the South-West Pacific.
12 charts have been updated (charts for Paraguay River) (DHN update 10/01/2011)- 3304 DA ISLA ARECUTACUÁ A ESTANCIA OLIVARES
- 3305 DA ESTANCIA OLIVARES AO PASO MERCEDES
- 3306 DO PASO MERCEDES AO PASO PALMA SOLA
- 3308 DO PASO VILLA REY AO PASO SAN JUAN
- 4411 DA FOZ DO RIO TROMBETAS AO LAGO QUIRIQUIRI
- 4412 DO LAGO QUIRIQUIRI AO LAGO PARU
- 4413 DE ORIXIMINÁ A ILHA JACITARA
- 4414 DA ILHA JACITARA AO LAGO AXIPICA
- 4415 DO ESTIRÃO DO FRANÇA AO LAGO ARACUÃ
- 4416 DO LAGO ARACUÃ AO LAGO BACABAL
- 4417 DO LAGO SAMAÚMA AO LAGO MUSSURÁ
- 4418 PORTO TROMBETAS
Today 233 charts (281 including sub-charts) from DHN are displayed in the Marine GeoGarage
The Discovery took Scott, Shackleton and other pioneers to Antarctica in 1901-02
Samples of a marine creature collected during Scott's Antarctic expeditions are yielding data that may prove valuable in projecting climate change.
The expeditions in the early 1900s brought back many finds including samples of life from the sea floor.
Comparing these samples with modern ones, scientists have now shown that the growth of a bryozoan, a tiny animal, has increased in recent years.
They say this means more carbon dioxide is being locked away on the ocean bed.
The tiny bryozoan, Cellarinella nutti, looks like a branching twig that has been stuck into the sea floor.
It grows during the period in the year when it can feed, drawing plankton from the water with its tentacles.
The length of the feeding season is reflected in the size of the annual growth band - just as with tree rings.
In the journal Current Biology, researchers from the British Antarctic Survey (BAS) have just published an analysis of growth rates in samples collected in the Ross Sea.
This is the Antarctic region where Capt Robert Falcon Scott moored during both the Discovery expedition of 1901-04 and the Terra Nova expedition a decade later, in which he lost his life attempting to return from the South Pole.
Feeding time
Other projects have since collected bryozoan samples at the same site, while the Census of Marine Life has increased the flow of data over the past decade.
Putting all this data together has allowed researchers to show that the creatures grew roughly the same amount each year until about 1990.
Since then, there has been a steady increase, with the annual growth rate now being more than double the 20th Century average.
The BAS scientists suggest this means that the bryozoans are now eating for longer, which means they are eating more phytoplankton - the tiny marine plants that draw dissolved CO2 from seawater.
"This is important because it's locking away carbon," said lead researcher David Barnes.
"The 'branches' of the bryozoans break off and are easily buried, and we've seen that - so burial is taking carbon out of circulation," he told BBC News.
The team suggests this is acting to increase the size of the carbon sink - the absorption and storage of CO2 - in the Southern Ocean.
However, other researchers have concluded that the Southern Ocean is progressively absorbing less CO2.
The Global Carbon Project, an international research network, concluded four years ago that the size of the global sink fell by 18% in the period 2000-06, with a large chunk of that decrease registered in the Southern Ocean.
"Winds there have accelerated over the last 50 years, and it's thought this is speeding up the mixing in the Southern Ocean and bringing to the surface deep water that's rich in CO2," said Corinne Le Quere, a member of the Global Carbon Project and director of the Tyndall Centre for Climate Change Research.
"So we have observations of this physical process, but the biological activity we don't have much information about; if you're mixing the ocean more, how are organisms responding?
"Usually in my experience the biological response compensates a bit, but not enough [to counteract the physical change]; and the fact that you have this one organism with higher growth rates doesn't say how much this is going to affect the carbon balance."
If the new research does not shed too much light on the likely progression of climate change, it does help us put the achievements of Captain Scott and his colleagues in a new light.
Despite the hardships inherent in polar exploration, both expeditions made the collection of scientific samples a top priority - including retrieving samples from the sea bed at a depth of half a kilometre using trawls.
"Prior to this, I tended to associate success in the Antarctic with people like Amundsen and Shackleton - Scott, I thought, doesn't have the same attachment to success," said Dr Barnes.
"But now I view things differently, and I think in 100 years' time people will still be using the collections he made - they're extensive and high quality, and in fact we struggled to find collections made after that that were as good.
"He really should be given more credit for some of the scientific work they did."
Links :
- BAS : Captain Scott’s century-old collections suggest marine life is capturing more carbon
Coral reefs are classified by estimated present threat from local human activities, according to the Reefs at Risk Revisited integrated local threat index.
