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Ancient forests

Ancient forests

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Ancient forests

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  1. Ancientforests Peter Shaw USR

  2. 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.

  3. 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 7000 Rainfall, mm/year

  4. 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.

  5. 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.

  6. 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..

  7. Where do rainforests occur? • SE Asia and Oceania – predominantly dipterocarp trees, very damaged now. Africa – the Congo (many families) • Pacific NW of USA (conifers) • Australia, Tasmania – small remnants of highly-diverse eucalypt (or Nothofagus) dominated forest. Wallace line • South America – The Amazon (many families)

  8. 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.

  9. 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.

  10. 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

  11. 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??

  12. 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).

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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-gatherer-gardeners shape forest ecology). Large scale farmers are always disastrous, at least for biodiversity, usually for the farmer too.

  21. Isn’t logging controlled nowadays? • Bluntly, no. Perhaps in Tasmania the logging companies more-or-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.

  22. 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 canopy-dwelling 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.

  23. 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.

  24. 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

  25. Brief case studies(that you probably didn’t want to know) Africa: • 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.

  26. 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.

  27. 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.

  28. 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.

  29. Orang pendekWWF Identikit picture 1m ish Confined to a small area of Sumatra – not yet officially acepted,, though seen by many good witnesses.

  30. 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 south-east 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.

  31. Climate Change 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. 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. Full warm interglacial Depth of ice age CO2 200 250 300 350 400 450 500

  32. 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