Oh no, not again: Climate Change Harms Endangered Species...?

It seems to be my fate to complain about "The intersection". Now lookit their latest post. The bottom line? global warming results in sea turtle decline (emphasis in the original). Its exciting news: the most dramatic link I've seen yet demonstrating how that pesky troublemaker climate change is likely harming endangered sea turtles.

Ah... but... there's a bit of a giveaway in there: its harming endangered sea turtles? Yes indeed, its the same old story: the biggest problem is current human damage and habitat destruction, GW is only a secondary factor, and a speculative one at that:

Many sea turtle populations are below 10% of their pre-Columbian numbers [1], [2], [3] and [4]. Though historic and systematic over-exploitation is the principal cause of these declines, sea turtles face similar threats today. Adults and juveniles are actively hunted and commercial fisheries catch them incidentally. Nesting suffers from beach development, egg poaching and the poaching of nesting females. Accompanying these familiar hazards is the largely unknown consequences of recent climate change. Here we report monitoring surveys from the Dry Tortugas National Park (DTNP, 24.64N 82.86W), Florida, and show that hurricanes and other storm events are an additional and increasing threat to loggerhead turtle (Caretta caretta) and green sea turtle (Chelonia mydas) nesting. Both species are listed by the US Endangered Species Act and the IUCN considers them 'endangered' abstract]

Sadly I don't have access to the original, because I'd be interested to know how they expand that "and increasing" bit (Nude Scientist provides some info: Nest destruction by storms seems to be getting more frequent. Between 1995 and 2004, the proportion of surviving nests dropped by more than half. In 2004, the final year of the survey, a series of category 3, 4 and 5 storms destroyed three-quarters of loggerhead and green turtle nests)

And if you want a hint as to how humans may be impacting these turtles, then looking at the pic in the post gives an idea: theres an elephant in the picture, oddly enough not arrowed: yes, the topmost island is largely covered by a vast hotel [Upadte: oh no it isn't; its Fort Jefferson, apparently. Thanks folks! -W]. I imagine that must have distressed some of the turtles and might have affected their reproduction.

OK, onwards. This has obvious connections to the Great Hurricane Debate. As RP Jr has pointed out many a time, most of the increase in damage from storms is due to more building on the beachfront. If you wanted to ameliorate future damage, the cheapest way is to build back from the shoreline a bit, or build sturdier buildings (actually, is that true I wonder? Given how valuable beachfront property is, perhaps reducing CO2 might be cheaper...). Anway, to proceed with the comparison before I get lost: if your goal is to improve turtle numbers, stopping people interferring with them and their habitat is best.

Over-hyping these connections is a bit of a shame because it seems likely that ecological problems are going to be one of the biggest harms from GW, and (barring Hansen's far-end predictions being about right on SLR, which is unlikely IMHO) about the most likely clear danger to come from a "dangerous" +2 oC within 100 years. Reading around the impacts stuff a little while ago at least half convinced me that was correct, but the impacts were more boring things than turtles.

More like this

Do you know the structure to be hotel? To my eye it looks more like an abandoned fortress.

[You may well be right - it does look more like that on closer inspection. My argument still holds. It may be this, but that doesn't really help -W]

This seems another example of the argument most cogently illustrated by Roger Pielke Jr.'s hurricane data: situations in which the threats associated with a given phenomenon are enormous and multi-faceted, and in which the added threat associated with AGW are real but marginal, but AGW gets all the attention because it provides such a useful opportunistic argument.

[Well expressed -W]

FYI, the structure in the picture is Fort Jefferson, never finished and set aside as a US National Park. Great diving area!

In the Tortugas post you linked, AGW may get more than its fair share of attention because its influence is unknown, and open to imagination...

> build back from the shoreline a bit,

And don't use those damned outdoor white lights (halogen and compact fluorescent even more than ordinary incandescent have a big emission spike in the blue-green (400-500 nm or so) that fools baby turtles into trekking toward the buildings instead of toward the moon rising offshore).


Buy the nice amber LEDs.

Stupid compact fluorescents. Bad for people too, if insomnia's a problem.

By Hank Roberts (not verified) on 05 Sep 2007 #permalink

harming endangered sea turtles? Yes indeed, its the same old story: the biggest problem is current human damage and habitat destruction, GW is only a secondary factor

Exactly Stoat. You repeat what I outlined at the bottom of the post.

the take home message of this post is that biodiversity on this planet, already in trouble, is now under even more pressure do to rising sea level, warming oceans, and factors like increased storm surges.

Thanks for reading and especially for reiterating the point.

"As RP Jr has pointed out many a time, most of the increase in damage from storms is due to more building on the beachfront"

I assume that doesn't apply to the Turtles?

>building on the beachfront

That's exactly where sea turtles build their nests, of course.


"After about 30 years of maturing, adult female sea turtles return to the land to nest at night, usually on the same beach from which they hatched. This can take place every two to four years in maturity. They make from four to seven nests per nesting season.... Incubation takes about 2 months...."

They have started showing up farther north:


"July 1, 2007
"ON A BRISK, WINDY NIGHT In April, a sea turtle heaved herself from the Atlantic and onto an Ocracoke beach.
She was big - 5 feet across - and heavy - more than half a ton, and the front flippers she used to drag herself across the sand were really made for water.

"But she had a mission on this deserted beach eight miles from anywhere. She crawled, slowly but surely, until she found a place some 50 feet from the high tide line that somehow felt right. She made herself a shallow pit and dug, one foot, two feet, three feet down, scattering sand over a patch of beach as big as two pickups. Then she was ready to do what she had come for. The leatherback sea turtle laid her eggs..... a leatherback, one of the most rare and endangered sea turtles in the world, a sea turtle that until 1998 seemed to prefer nesting on tropical beaches. That year, the first leatherback nests were confirmed in North Carolina on Cape Hatteras National Seashore...."

By Hank Roberts (not verified) on 05 Sep 2007 #permalink

We have had Leatherbacks nesting on Ocracoke before - from memory, we had 2 in 2000, and one on Hatteras Is. Hatteras is to the north of Ocracoke, and at least one more in 2003 I believe.
The nest this year on Ocracoke did not produce any hatchlings. It was excavated at 90 days and a few eggs had what appeared to be ~20 day development, so we reburied the remainder and to date none have hatched. The two on Ocracoke in 2000 were lost to an "early" Nor'Easter which caused overwash and sand deposition on the nests, efectively drowning the embryos. The 2000 nest on Hatteras did hatch, but IIRC, it had low productivity.
If sea-level rise is not attributable to AGW, then no, global warming is not effecting nesting sea turtles. Not only should you think about storm surge, consider bi-monthly Spring Tides.
And complicating all of this, is not only development on the beaches, but manipulation of the habitat as well. The Outer Banks has ~80 miles of beach, which is reached by driving ~80 miles of highway. That highway only exists because of the dunal system created to protect it.
Those dunes cause beach narrowing and erosion and cause sub-optimal nesting locations for sea turtles.

Don't get me started on nesting shorebirds.

By wildlifer (not verified) on 05 Sep 2007 #permalink

">building on the beachfront

That's exactly where sea turtles build their nests, of course."

Sorry, I meant that the increased storm damage to turtle nests is presumably not attributable to increased nest building on the shoreline.

However, as wildlifer points out, if the human construction forces the nests to be built closer to the (mean) tideline then it eventually becomes a double whammy with SLR being (currently) the minor blow.

Your 'vast hotel' in the picture is indeed Fort Jefferson, which was built as a military fort (in 1846) and then became a Union army garrison in the Civil War. Since the early 1900s the islands have been primarily a scientific outpost. Never a hotel. There has been little development since the fort was built, and that only research shacks. Pilke is right that recent coastal development is an artifact in many claims of increasing storm damage. But Pilke's argument is mainly about compensating monetary damage and rebuilding(e.g. "damage from hurricane Katrina is estimated at US$125 billion). The Dry Tortguas is not like much of coastal Florida (or elsewhere in the in Caribbean) where turtles nest. There are no night light issues, no construction digging up nests close to the sea, no ATVs, no wild hogs digging up nests to eat eggs, etc. It's remote. So they don't have the threats that may be associated with coastal development, of the kind Pilke's good work notes. The paper says federal researchers and volunteers examined each nest and noted when they were washed away from storms entirely, or when storm surges flooded buried nests. These effects seem the observations of many people. And though any observation may not be perfect - science isn't! - the paper makes no overarching claims. The cause does not look speculative.

By gatorzrule (not verified) on 06 Sep 2007 #permalink

Gabrielle is headed right for us, even just as a TS it's going to create havoc, we're taking the initiative to excavate turtle nests which are in the process of hatching to prevent them from being either washed out, or covered with too much sand.
There are at least 20 nests we could lose, as relocation isn't possible at this time.

By wildlifer (not verified) on 08 Sep 2007 #permalink