Transcript Document

Ancient
forests
Peter Shaw
USR
Introduction



I hope that you all know, in general outline, that there is
a conservation concern around tropical rainforests. In
fact this is part of a wider set of concerns around
ancient forests globally.
The issue of rainforest conservation is one of the
losing battles in global conservation. Despite all the
good intentions, we are losing these habitats
alarmingly rapidly.
Today I want to introduce the ecology of ancient
forests, then examine the pressures on them now, and
those that we can predict for the future.
When is a forest a rainforest?

Technically forests are classified by rainfall level.

Rainforests are forests where rainfall exceeds
4000mm per year. Moist forests are 2000-4000 mm
per year, below this are dry forests.
Dry forest
moist forest
true rainforest
often called r.f.
0
1000 2000 3000 4000 5000 6000
Rainfall, mm/year
7000
Dry forests
In fact dry forests are generally the most endangered, as
the land is easier for humans to colonise. Tropical dry forest
has all but ceased to exist in most areas due to human
pressure. Rainforests are much less welcoming, so have
survived better. Most rainforest plants are evergreen, while
dry forest species tend to be deciduous.

Some truly amazing biodiversity
clings on in the dry forests of
Madagascar, where sifaka lemurs
jump between savagely spiny
endemic thorn scrub (endemic
family, Dideriacae), alongside
endemic chamaeleons and
tortoises. This has minimal value
as timber but is prone to clearance
by farmers, grazing by goats etc.

Guanacaste national park,
Costa Rica
In South America there are few intact areas of dry forest, indeed
in the small country of Costa Rica the dry forest was all but
destroyed. It used to cover most of the current farmland, with
only a few individual old trees hanging on in stream-edge cliffs.
No big iconic species, just a lot of endemic plants and
invertebrates.
The job of saving and restoring it fell to Dan Zanzen, who set up
the Guancaste national park. The first job was to protect the
surviving fragments (pockets or individual trees by water
courses, too unstable to farm). This meant controlling grazing
pressure and preventing any further tree cutting.
Tree nurseries
Once surviving pockets were identified, seedlings were collected
and propagated in tree nurseries. These were guaranteed locally
adapted stock. For several of the leguminous trees, the best way
to propagate them was by feeding ripe seed pods to ponies, then
letting the ponies wander free a while! There used to be native
megafauna able to disperse seeds, exterminated by humans whose
horses later fulfilled the same role.
The reserve is currently stable, with its main threat identified as
fires started by neighbouring farmers..
Where do rainforests occur?
SE
Africa – the
Congo (many
families)
Pacific
NW of
USA (conifers)
Asia and
Oceania –
predominantly
dipterocarp
trees, very
damaged now.
Wallace line
America –
The Amazon
(many families)
South

Australia, Tasmania – small remnants of highlydiverse eucalypt (or Nothofagus) dominated forest.
USA




The pacific NW coast of the USA hosts
unique forests of giant conifers.
Redwoods, sitka spruce, douglas fir,
lodgepole pine.
The biomass per m2 here is greater than
anything tropical, with 90m stems the
norm.
A Yanomami indian chief flew over the
logged area in the 1990s, and noted the
damage was far worse than anything in
south america.
The area has been logged since
‘discovery’ last century, and only 5% of
virgin forest area survives. Entire
communities depend on logging for
income. The trouble is that the regrowth
forests are not growing fast enough, and
lack the biodiversity of old-growth forests.
Spotted owls




The arguments have been brought into
focus by the plight of the spotted owl, an
endemic confined to old-growth forests.
In the early 1990s it was declared an
endangered species by the US
government, preventing loggers working
in forests where it occurs.
“Save a spotted owl, starve a logger’s
child”.
A compromise was reached in 1993
under Clinton & Gore, allowing a limited
amount of logging but greatly reducing
extraction from old growth forest and
creating sanctuaries. Needless to say
neither side was happy.
Other north-western
specialities
Actually compared to tropical systems these pacific north western
rainforests are species-poor, but they have some useful iconic species.
There is an auk which nests in hollow old conifers, the ancient murrelet.
A primitive rodent, the mountain beaver or Sewell is arguably of greater
biodiversity significance. Plus the usual bears wolves puma moose etc.
Mountain beaver
Aplodontia rufa
Ancient murrelet
Synthlibormaphus antiquus
So is Sitka good, or bad?
Sitka spruce forests support spotted owls,
murrulets, bears deer mountain lion etc, and their
replacement by secondary forest is unquestionably
bad.
So why is it that UK conservationists get upset
about Sitka being planted all over our upland
bogs??
Tasmania


Has strange, remote rainforests
including some of the tallest trees
in the world (Eucalyptus regnans).
Protests over plans to dam the
Franklin river and flood large areas
of forests led to international
protests, and mass arrests (of
David Bellamy among others).
Tropical rainforests


These are thought to contain the majority
of species on the planet.
Their species richness is hard to
comprehend for naturalists used to
European levels of biodiversity.




Tropical forests average c. 80 tree
species per acre, vs 4 in the UK.
Brunei and sarawak have 2500 tree
species – the UK has twice the land area
and 35 tree species.
The collector Henry Bates recorded 80
species of butterfly within a few minutes
walk of his camp. The whole of the UK
has 55.
The planetary species total went up from
2 million to 30 million when estimates of
tropical beetles started to firm up.
Giant “emergents”
Idealised structure
of a rainforest.
Canopy 30-40m up –
evergreen leaves, many
epiphytes. This is where
most of the biodiversity
resides.
Ground level – dark (2% light),
humid little evident life, fluted
boles.
Why so much life?




This is still far from clear, but there
are certainly several factors
involved:
Site age
a proliferation of micro-habitats
ice-age refugia.
Rainforest age




These are as old as terrestrial ecosystems
can be – apparently dating back to the K/T
boundary event, at least in places.
This gives potential ages of 65 million
years. UK forests cannot be over 10,000
years old.
In this time their species richness has
burgeoned, while the soils have become
intensely leached.
Rainforest around mayan temples is clearly
different to surrounding virgin forests – and
the temples were abandoned >800 years
ago. These are long-term systems.
Micro-habitats



Each tree supports dozens
of micro-habitats, mainly
associated with its epiphytic
plants.
Epiphytes are plants that
grow on other plants. Some
of the better known such
plants include bromeliads,
orchids, and ‘jungle cacti’
(Epiphyllum, Christmas cacti
(Schlumbergeria).
Lianas bind the canopy
together
Refugia


In fact we do not believe these forests to
have been unaffected by changes in world
climate - large areas dried up during the ice
ages. But there were isolated pockets, often
in river valleys, which remained wet and
acted as refuges when the planet dried.
There are the pleistocene refugia, and are
invoked to explain why biodiversity is
especially high is some pockets of forest.
These pockets of highest diversity are where
climatologists tell us that forest would have
persisted.
Rich and fertile?


If one spent 60 million years
digging manure into a soil, it would
become exceedingly rich and
fertile. This is not true for these
ancient forests - they have spent
60 million years removing nutrients
from the soil. What remains in the
ground is largely iron-aluminium
oxides, with minimal fertility. The
nutrients are held in the biomass.
Corollary - remove the trees, the
system will regenerate poorly if at
all.
LOGGING!



This causes direct damage, and even low-impact logging
opens up trails into the forest which hunters use to exploit
“bush-meat”.
The remaining soil often turns to laterite - like red cement,
useless for agriculture or forest.
Logging goes hand-in-hand with the encroachment of
farmers. Small-scale farmers may be a problem, or may
even increase diversity by leaving old gardens to revert to
jungle (the “swidden” model where hunter-gatherergardeners shape forest ecology). Large scale farmers are
always disastrous, at least for biodiversity, usually for the
farmer too.
Isn’t logging controlled
nowadays?



Bluntly, no. Perhaps in Tasmania the logging companies moreor-less stick to the permits given them by the state government
(though they keep being given generous permits to continue
logging virgin forest).
In most of south america there simply isn’t any formal control;
the Brazilan p.m. admitted that 23,000 km2 per year were being
illegally cleared,and promised satellite mapping to control the
situation.
Indonesian logging is so blatantly illegal that Greenpeace have
taken to trying to board shiploads of Indonesian timber at
Tilbury (March 2004), and the whole country has been
recommended for a boycott by the Rainforest Action Network.
Logging effects:
Long before logging has cleared land, its biodiversity value will have
declined. Even “sustainable” logging must cause environmental
change locally; the idea is to remove a few large trees, but this will
change the microclimate and cause immense disruption to all animals
whose territories overlap the emergents in question.
Loggers tend to have guns, and any large fauna is likely to be shot at.
Their roads cut swathes that form uncrossable barriers to canopydwelling creatures. The worst long-term damage is almost certainly
the fragmentation effect. Once a population is confined into one small
area it is far more likely to go extinct, and clearly cannot then come
back. This is a particular concern for large mammals, which
inherently need large tracts of continuous land.
The Manaus fragmentation
experiment
A long-term experiment was initiated by Lovejoy in the 1979 in Manaus,
Brazil. Blocks of forest were cut into isolated blocks of differing areas
(1, 10 or 100 ha), leaving the sharp edge typical of commercial
clearance.
As time has progressed, the continuous forest species of all groups
vanished from the small plots; they could not stand proximity to the
edge. Even the largest blocks showed edge effects at their centre and
omitted some forest-depth invertebrates.One group of 6 white faced sakis
hangs on in a 10ha block – for how long? 2 bearded sakis in a similar
patch vanished, presumed dead
Bizarely, as time progressed the cattle ranches were abandoned and
species-poor secondary forest has started to recolonise. It is too early to
say what the long-term trend will be.
Relaxation curves :=(
This is a nice-sounding term for a ghastly process. A habitat island of a
given area has some equilibrium species richness; introduce a
fragmentation effect and the equilibrium species richness falls to a new,
lower level. This means some species go extinct, at least in their local
subpopulation.
This process takes time though, with non-viable populations hanging on
for decades. In the case of forest trees the “hanging on” will be
centuries.
Species richness
So after a forest undergoes
fragmentation, as graph of its
species –richness against time
gradually “relaxes2 to a lower
level.
disturbance
Time, years
Brief case studies
Africa:




(that you probably didn’t want to know)
Gorillas - 2 species, Chimpanzees - 2 species, okapi
(discovered c. 1910), congo peacock.
Experiences chronic political instability, being a country
awash with poor psychopaths armed with modern weapons.
This is probably good for conservation in many ways, but is
ruinous for large mammals and leads to a near-total lack of
control on sustainable logging.
One thing, among many, that makes me ashamed to be
human is African bushmeat. I don’t mean cane rats or
bushpigs, I mean eating our closest relatives, gorillas and
chimpanzees. The tactic is easy – hunt with dogs to scare
the animals up trees, then blast them down with
kalashnikovs. Bits of ape head, hand etc get smuggled into
Heathrow on a regular basis.
japanese logging firms are exploring the Congo. Luckily the
territory is still dangerous.
South America
Amazon you think, and of course it is still the greatest continuous sheet
of forest left on the planet. It appears to be growing disproportionately
fast as CO2 rises, helping reduce greenhouse effects.
But just to make the point about habitat diversity occurring in localised
areas, I’ll use the Golden Lion tamarin (GLT) as an iconic species from
a much more endangered forest, the Brazilian coastal forest. Since it
occurs near the coast, where people prefer to live, it has suffered
disproportionately from clearance, being down to <9% of its pristine
area, and much of that fragmented.
Elsewhere in Brazil, the issue has been land clearance for cattle farming.
Chico Mendes was a rubber tapper killed as he tried to protect the forest
from land development.
Australasia
rainforests in this region cover a small region of Australia’s north
and east coasts, plus much of New Guinea. There is a famous
dividing line between this region and South-east Asia, known as
the Wallace line. The to south/east you get marsupials, birds of
paradise, eucalypts, while to the Nw you get placentals and
dipterocarps.
Asia
The dipterocarp forests of Asia include some of
the biologically richest and most damaged habitats
anywhere; species richness of most groups is
higher than Africa, with iconic species likely to go
extinct in your lifetime.

Orang-utans (2 species, Bornean and Sumatran), may hang on
in captivity after forests are destroyed. An estimate from 2002
was 7300 Sumatran orang utans remaining, and a population
decline of 1000 per year ish throughout the 1990s.

There may well be an unknown anthropoid in this region- Orang
pendek, reliably sighted several times in malaysia.
1m ish
Orang pendek
WWF Identikit picture
Confined to a small area of Sumatra – not yet
officially acepted,, though seen by many good
witnesses.
Forest rhinos
You have seen rhinoceroses, big animals on open plains. Yes, three
species do that. The other two species live in dense forest, in southeast Asia, and sadly are probably doomed to vanish this century. Their
ultimate problem is that they won’t breed in zoos. One of the few to
survive capture any length of time only ate alfalfa soaked in marks and
spencer tropical fruit juice!! Since they won’t breed in captivity,
capturing members of the wild population would be worse than
useless, and all we can do is try to protect their forests.
Javan rhino: 10 in
Vietnam, 70 in Java
as of 2004.
Sumatran rhino:
300 in Sumatra, as
of 2004.
Climate Change
This is not a problem if you
can skip the next 200,000
years (by which time things
should have settled down
again).
Biodiversity can’t.
CO2 200 250 300 350 400 450 500
The most serious long-term
threat to all the forest systems
I have mentioned today is,
IMHO, climate change. As
we continue to pour our CO2
at 7GT C/yr the climate will
assuredly warm up.
Full warm interglacial
Depth of ice age
Effects of climate change on
tropical forests?
We’ve started to see it: terrible fires as drought kills timber leaving
land vulnerable to fire. Fires in the forests of Borneo in 1997/98
spread smoke across much of SE Asia, putting 200,000 people in
hospital with respiratory problems. And these were thousands of
miles away. The effects on Orangs etc must have been terrible.
The problem here was peat forests drying out; once peat starts to burn
it smolders for decades.
If the same thing happens to the
Amazon the carbon released will
be such a sharp warming pulse
that we will confisdentlty lose
control of our climate, probably
releasing methane clathrates and
taking us to conditions warmer
than any time in the last 55 million
years.
Smoke trails,
Borneo 1998