Transcript Marine Conservation

Marine Conservation
Peter Shaw
(with thanks to Claire Ozanne and Martin Speight)
Issues to cover:
Marine biodiversity – hotspots and global significance
Fisheries – Zuckerman’s paradox
Coastal land use changes
Pollution
Solutions?
Marine biodiversity
We know of c 300,000 species in the sea, including all known
phyla (except velvet worms Onychophora) – guesstimates are
quoted at 500,000 species in total, rather fewer species than on
land (lacking the hyperdiversity of insects or orchids).
Endemism is more difficult in the sea as it is interconnected
(consider lakes, mountain ranges by way of comparison), but
endemics do occur, especially in delimited zones such as the
Red sea..
To the best of our current knowledge, the highest species
richness of any marine habitat is found in tropical coral reefs,
systems built on the calcareous skeletons of colonial anthozoa.
Coral reefs
These occur within 20 degree of the equator in seas between 20
and 28C. Given this and their need for clear shallow water
(<25m, exceptionally <100m) they cover about 1% of the earths
surface (compare 14% for primeval rain forests).
Despite this estimate are around 25% of all marine species and
75% of all fish species. One fish expert (Gerard Allen, Perth
museum) broke his own record for species in one scuba dive
twice in one spot off Irian Jawa: 281 and 283 species
respectively!!
There are under-studied communities inside the coral rubble,
where divers cannot go, that appear to be very species-rich.
Like rainforests these are inherently infertile systems, and many
species are forced to live symbiotically – including the corals,
90% of whose energy comes from algae living within their
tissues called zooxanthellae.
Coral reef map
Coral reefs shown in yellow
Bleaching
These algae prove to be the Achilles heel of the reef, since they impose
limits on the corals. They need light, hence the need for clear water.
Anything which decreases light penetration hurts the corals, hence
ultimately the whole reef community. Soil erosion is a common and
serious nuisance here, as the agricultural runoff (it’s usually agricultural
runoff) not only makes turbidity but is fertiliser-enriched, leading to
explosive algal blooms that smother the corals.
If the sea temperature exceeds 28C the corals undergo a process called
bleaching in which they eject their symbiotic zooxanthellae (algae who
live symbiotically in the polyps), an act which usually (not always)
proves suicidal. As the greenhouse effect bites, reefs all over the planet
can be predicted to bleach. A second, potentially more serious issue
ocurs at 1500ppm CO2, when calcium carbonate will cease to precipitate
out of solution.
Tourists often admire the pretty white coral skeletons…
Bleaching was
first recorded in
the 1980s, but is
now a
widespread
threat.
How about more direct impacts from people?
Fishing sensu latu clearly impacts on reef ecology,
by removal of selected target species. We will cover
the economics of fisheries soon.
Not just fish: The giant triton (Charonia tritonis) has
a handsome shell for which it is harvested. It is also
a major predator on crown-of-thorns starfish, which
in turn damage coral reefs badly.
Sea cucumbers (holothurids) aka trepangs aka beches de mer are
stripped by fishermen, collecting for the Asian market ($2 each).
An invasion of trepang fishermen into the Galapagos islands, and
the subsequent enforcement of fishing regulations, led to street riots
that threatened to burn down the Charles Darwin research centre in
the Galapagos in 1997. Nine giant tortoises has their throats cut.
We will look at the Galapagos spiny lobster fishery soon, which also
led to serious violence .
Dynamited reef
Other influences on a reef system:
If you’re lazy and careless you throw in cyanide
(which kills everything) or dynamite (which destroys
most animals and the structure of the coral). These
can only be condemned – are nowhere legal but
prosecutions are uncommon.
How about divers? Divers are always taught not to
touch, not to disturb, not to interfere (usually not even
feeding fish). But divers come in great numbers – on
some busy red sea reefs (Hurghada, Sharm el Sheik)
divers come and go in an endless stream.
Some dive practices are certainly bad: anchoring
to the living coral causes serious mechanical
damage. Responsible diver operators set up fixed
anchorages. In the Red sea in 1992 the operators
dropped anchors on live reef, hating having to do
it, since any permanent fixtures (even underwater
ones) were stolen :=(
Diver touching
coral – note the
snapped edges
Recent studies in the Red Sea show that coral
damage by tourist boats and divers could be
considerable, although minimised by responsible
briefings (Medio et al., 1997; Jameson et al.,
1999). Damage is usually caused by careless
Boat-damaged
accidental scraping of fins across living coral,
coral, Australia
although sometimes branches are snapped off.
Divers generate plastic litter – esp mineral water bottles. Future
archaeologists will call us something involving plastic and detritus…
Fisheries
Of all the examples of human failure, our inability to
regulate fisheries into sustainability must rank with our
inability to predict earthquakes as a long-running
tragedy that science seems unable to help with.
As a good approximation, if it’s worth money and lives
in the sea it must be assumed to be potentially
endangered!
Zuckerman’s paradox
• Actually I made this name up, though the
paradox was stated by S. Zuckerman in 1992.
It is not widely stated, still less understood!
• In essence it states that under a freeZuckerman S
(1992).
Between
Stockholm &
Rio. Nature
358, 273-276.
market system non-renewable
resources tend to be harvested
sustainably, while valuable biological
resources tend to go extinct.
Examples:
• In the 1970s a report called ‘Limits to growth’ was
published, predicting economic collapse before the
millennium due to reserves of oil, copper and other
minerals running out. At the time the planet had 20
years supply left of these non-renewables.
• In 1992 the world bank reported that these minerals, +
others, were cheaper than they had been 20 years
previously.
• Why? Because free-markets are self limiting. As a
resource becomes scarcer its value goes up, so it is
worth deeper mines / offshore drilling etc. Minerals
don’t go extinct, they just become harder to extract.
At the time the Limits to Growth report came out, there was a
huge, healthy cod fishery on the Grand banks off
Newfoundland. This had been discovered hundreds of years
ago, was among the largest fisheries on the planet, and could
be harvested sustainably for ever.

The Grand Banks remains closed to fishing, and has been
since 1995- the stocks are exhausted and failing to recover.


WHY??? – Because it is economically rational to over-fish.
The majority of fisheries policies have been based on a
theory called MSY – the Maximum Sustainable Yield. This is
turn is built on a logistic model of population dynamics.
Almost invariably the model has mandated one target level,
and politicians have then taken a compromise position
between that target and what the fishing industry requested.

Reasons why MSY theory
doesn’t work too well in
practice:
• 1: Populations don’t obey the
logistic equation
• 2: Fishermen harvest money, not
fish.
The logistic equation doesn’t work!
• It predicts that once a species is reduced from K
to a lower level, that population will always
bounce back to K. This is often not true –
competitors step in to fill gaps, effectively
reducing K.
• W. coast USA has many salmon rivers – in one
runs a biennial fish, the sockeye salmon.
Because of the 2 year life cycle it has isolated
odd- and even-year populations. In one river
system one year over-fishing combined with
drought to wreck the population – it never
recovered. To this day there is a large difference
between even-year and odd-year populations.
Harvesting money
• This is where it REALLY goes wrong!
• The problem is the link between economics and ecology –
or rather the total lack of any.
• It is straightforward to produce a little economic model
based on catch per unit effort, return per catch, and fixed
costs of harvesting to show that – for an economically
valuable resource - there is a critical population size N0
below which it is not rational to harvest. Above this
population size you will make money.
• This critical population size does not depend on the MSY –
if N0 <MSY it is “rational” to over-exploit the population.
N0 = Catch per unit effort /(return per unit harvest * catchability)
• What N0 does depends the economic value of the species. If
value is high, it is worth harvesting to very low population
levels. The problem is that economic value can change – a rare
species may become worth more as consumers pay a
premium for scarcity.
• In practice, what has happened time and again is that a new
fishery is started – large population, easy to harvest, easy
money. Extraction starts in earnest, the population declines –
but the public get a taste for the new fish and its value goes up.
Extraction continues, population declines – but demand holds
up so the price goes up. Repeat the cycle until the fishery
collapses.
Fishery yield
Fishing
effort
Idealised graph of a fishery
collapse
• Salmon from Alaska.
• 1880 commercial fishing began. Most were canned - the
resource was seen as inexhaustible. Peak commercial
exploitation was 1936, then declined.
• 1900: 200 boats, harvesting 15000 salmon each
• 1950: 1000 boats, only catching 1500 salmon each.
• Thus more and more men chased fewer and fewer fish makes no biological sense, but value of fish rose in real
terms by x3. (Salmon are now expensive. In Victorian
London workers went on strike because they were fed up with
being endlessly fed on salmon).
• Why? Ecological madness, but economic sense BECAUSE
THE RESOURCE BELONGED TO NO-ONE. If it were
privately owned, the owner would protect the stock. As a
public resource, if you don’t harvest, someone else will.
Canned salmon
Alaska 1880-1975
Nth Pacific sardines
1910-1970
Spiny lobsters in the Galapagos
More trouble from the Galapagos, following the trepang riots
of 1997.
In 1999 there were 500 fishers of Spiny lobsters with a 54 ton
quota. These made money, and in 2000 there were 949
fishermen, who hit their quota in 2 months. When denied
permission to continue fishing they rioted, and destroyed all
the contents and records of the Charles Darwin research centre.
The Ecuadorian government sent in its special forces to rescue
the staff at the centre. Sometimes I’m ashamed to be human.
In the end the government set an 84 ton quota, against the
conservationists advice – a partial sell out.
Cod!
Cod Gadus morhua, staple of your
corner chippy, eaten in this country
for at least 2000 years, is so overfished that the north sea cod fishery
should really be shut down. Of
course, fishermen object because
that’s their livelihoods gone. And
as cod decline to uncatchability, I heard a food marketing person
explaining how we should grow to like eating other fish, such as Orange
Ruffy from deep waters around New Zealand.
And the population dynamics of this deep-water fish? It takes 25 years
to reach maturity, lives to 100 years. It’ll be wiped in a decade of serious
fishing. (Similarly for the Patagonian toothfish, 3500m deep in the
southern oceans, with 100,000 tpa taken illegally each year (as of 2003).
As a consequence of what I have just told you, I am unable to
avoid predicting that any high-value marine species in danger
from over-fishing. Bluefin tuna is regulated by CITES due to
its value in Japan ($24,000 for a single top-class fish, taking
60% of world tuna catch). Squids are harvested with industrial
efficiency by ships using light traps. As a by-catch, albatrosses
are regularly caught on the kilometer-long multi-hooked
fishing lines, to the extent that extinction of species is a real
possibility.
The best hope is the observation that the sea is a very big place,
and it is much harder to find and kill the last few members of a
species that on land. The time-honoured pattern is for species
to decline to near-extinction then hang on at low levels (great
whales being a classic example).
The disaster stories
There aren’t as many of these in the
sea as on land – as I said, the sea is
a big place. But there area few. No
fish have been exterminated in the
sea yet AFAIK (plenty in isolated
lakes – Rift valley cichlids
providing many examples). But
mammals and birds can’t make that
claim.
How about Stella’s sea cow Hydrodamalis gigas, confined
to the seaweed beds of Katchatka / northern Japan? It was
the largest sirenian ever known, toothless, mashing algae
between keratinous plates. It was also slow moving fat and
fearless of humans. Discovered 1741, extinct 1768. (The
other 4 sireneans are also all endangered)
Great Auk
Alca impennis
• Variously known as garefowl or penguin
(from Cornish for “white head”), this
flightless auk was found around the northern
Atlantic. Its pictures were painted in the
Grotte Cosquer in the Mediterranean c.
20,000 BP.
• It was only harvestable on its nesting
grounds – offshore islands, where thousands
of birds nested together. Sadly, thousands of
large, oil-rich, tasty flightless birds gathered
together to lay eggs proved to be just too
tempting.
Europe..
• Had exterminated all its great auk colonies by 1697,
except one on the tiny island of St Kilda. The last bird
here was trapped by the locals who accused it of being
a witch, and beat it to death in 1840.
St Kilda,
high street
1840
America
• Had huge auk colonies on its “funk
islands” off the eastern seaboard – auks
shoulder to shoulder for miles. Marine
charts noted their location as the din could
be heard for miles and was useful for
navigating in mist.
• These were close to where trans-Atlantic
ships landed, and were ruthlessly harvested
for fresh meat and eggs. Conveniently, the
great auk’s stomach is just big enough to
hold the fat rendered down of the birds
body. Fat-filled stomachs fetched money
as fuel for lighting.
• The cruelty and wastefulness of these
harvests was barbaric - it was an
unregulated free resource.
• The last east-coast rookery went extinct in
1802.
• The last population of Great Auks lived off Iceland. Up to 1800s they
nested on an inaccessible volcanic island Geirfuglaske, but this was the
centre of an eruption in 1830, and the birds moved to the relatively more
accessible island of Eldey.
• Then a merchant called Siemson realised that auks had a significant
market value, and made money by killing and stuffing birds from Eldey.
• By 1843 he had killed and sold 75. The last pair, a male and female,
were killed by being clubbed on Monday 3 June 1844. The species was
extinct.
• Note the ratchet effect here – as birds became scarce their value
increased, so they were more worth hunting.
Eldey – on a calm day
Food chain keystone species
More than on land, marine systems often have one
highly productive keystone species which feeds
the rest of the food chain. In the north sea this is
the sand eel, in the northern atlantic it is the
capelin, in the southern oceans it is krill.
What happens when you deplete this keystone species? Its
predators must reduce in numbers.
There is concern for krill – recent work from the BAS shows krill
numbers on the Antarctic peninsula to have declined in last
decade; these crustaceans feed on algae on underside of icebergs.
They feed penguins and whales.
UK seabird disaster 2004
We have a real conservation disaster this year, probably
beyond the control of any conservation bodies, or even
governments. It concerns our northern seabird cliffs,
ecosystems relying on sandeels. These fish are the
subject of an “industrial” fishery, harvesting their bodies
for oils (fuel) and cheap meat for fishfood etc.
A combination of overfishing and warming has led to
cold water fish all but disappearing from the north sea:
Cod and Sand Eel being especially significant.
(Haddock are doing better – so far).
Worse, far worse, is the impact of sandeel shortages on
breeding seabirds. “This year the cliffs of these
Northern Isles fell eerily silent and 10s of 1000s of
seabirds failed to rear any young” (RSPB, Atumn04)
Land Use Changes
Marine conservation? Land use changes?
Is this the correct lecture? Actually yes. I
have already mentioned the deleterious
Mangroves showing
impact of agricultural runoff on coral reefs. pneumatophores
There is another one, linked to mangrove
swamps.
Mangroves are among the few
angiosperms which flourish in salt water,
and form dense species-rich inter-tidal
forests (mangrove swamps), valuable in
themselves and as nurseries for young reef
fish.
These are cut for BBQ charcoal, and
replaced by aquaculture.
Shrimp farm cut into
mangroves
These mangrove swamps are being
depleted by conversion to commercial
shrimp farms. Not only does this remove a
valuable habitat but the shrimp farm
requires major inputs of fish food, which
eutrophies the water body and endangers
offshore corals. Mangrove swamp used to
shelter coastal communities from the full
force of hurricanes – one reason that
THE BRUTAL SUPERhurricane deaths have been so severe in
CYCLONE OF ORISSA
India and Africa recently is the replacement
Super-cyclone with winds 260of coastal mangroves by shrimp farming.
Greenpeace have a report (Hagler 1997)
called Shrimp, the devastating delicacy,
about the environmental damage caused by
the expansion and intensification of shrimp
farms.
300 km/hour (hurricane
category 5) hit the 90 mile
coast of Orissa with a
storm surge that created the
Bay-of-Bengal water level 30
feet higher than normal,
causing thousands of deaths.
Pollution
Anthropogenic pollution
What can you usefully do about marine biodiversity?
Not very much really, but there a few small tips:
Express a consumer preference for farmed fish over wild-caught fish. (I
know that these cause local pollution, but local pollution is better than
global population collapse. I also know that fish-farmers tend to feed
their stock on wild fishmeal, sadly. …).
Best avoid Tiger Shrimps – and make sure your BBQ charcoal is locally
produced.
Don’t buy animal souvenirs on holiday.
And don’t buy shark fin soup, and tell your friends not to. Sharks are
especially sensitive to harvesting pressure, and the method used is to
hook the shark, chop its fins off and throw it back to starve.
On a bigger scale, there are useful (if unpopular) actions to
take. The best appears to be the creation of marine
reserves, areas where fishing is simply not permitted. This
is usually deeply unpopular with local fishermen, but
recent work in the Catribbean by Callum Roberts (York)
has shown that the creation of large marine reservces does
not in fact reduce fishermen’s overall long term catchm,
and that the proportion of large (trophy) animals increases.
They grow up safe in the reserve, then some spill out of
the boundary into the fished waters beyond.
Roberts CM et al (2001) – effects of marine reserves on
adjacent fisheries. Science 294, 1920-1923.