funding for this program is provided by annenberg media. narrator: estimates on the total number of different living organisms that inhabit our planet range from 8 million to 60 million or more. of these, only about 2 million

have been described scientifically. there are a lot yet to be discovered. many of these discoveries could be made in tropical rainforests, where it is thought that over half of the world's species exist. but we are losing these bastions of biodiversity before we even know what's in them. and tropical biologist bill laurance is learning what impact en amall road can haven their viability. a lot of tree mortality, a lot of deaths. narror: the oceans, too small changes in a fragile coral reef ecosystem can have lasting effects. ecologist jeremy jackson is finding human impact on the world's oceans could be setting them on a path of drastic change that he calls the rise of slime. dr. jackson: if the world becomes a world of slime

then there's not much room for people. narrator: these studies -- one on land, the other in water -- are showing just how delicate ecosystems are and what an important role biodiversity plays in their ability to endure. just over 15 miles from the heart of panama city, and steps away from the panama canal, lies soberania national park a 55,000-acre rainforest that is just one of the many rainforests around the world being studied by tropical biologist bill laurance. dr. bill laurance: the focus of our research is, essentially how do humans affect tropical rainforests?

about 40 million acres of tropical forest are being destroyed every year. that's about 80 football fields a minute and as a consequence we are seeing vast landscapes being denuded of forests. we are also seeing the original rainforest being chopped up into isolated islands or parcels. and this might seem like an ironic place to talk about it here because it seems like such a beautiful area. we are in the heart of panama in soberania national park but this is probably the future of much of tropical biology, because although it seems like a large area of rainforest over here we have bulldozers knocking down the forest. over in this direction we have slash-and-burn farming going on. we have hunters encroaching from all sides of the forest having major impacts on the wildlife communities. this is an island of forest, and it's shrinking over time. and so really this is the heart of t question we are trying to get out here. are these going to be islands of survival or islands of extinction? yes, you're very cute. narrator: for laurance e importcef the rainforest arose from a lifelong love of animals.

very pretty little bird. dr. bill laurance: i was one of those kids at just loved animals. and i raised mountain lions and bear cubs, and i was a falconer. i had birds of prey and owls and ferrets and flying squirrels -- just a whole menagerie that my long-suffering parents put up with. i started working in zoos in the united states. and eventually i just became convinced that it's the protection of the natural homes the ecosystems that's really critical. so at that time i decided that i wanted to work on conservation of natural ecosystems. [ speaking foreign language ] narrator: that desire has taken laurance all over the world. for over 25 years, he has beestudying rainforests in africa, australia, brazil, and at the sthsoni tropical research institute in panama. dr. bill laurance: we do some work here in panama but the amazon and central africa where we work are just such hot spots of forest destruction.

in the amazon, there is incredible forest destruction for cattle ranching. there's a huge explosion in soybean farming. there's massive logging operations. there's an avalanche of new highways and roads and other kinds of projects which are creating a lot of problems for the forest. we focus on those areas because they're the most important from a conservation perspective. narrator: often called the lungs of the planet, the world's rainforests have gone from covering 14% of the earth's land surface to 6% over the last 50 years. in addition to providing us with over 20% of the oxygen we breathe these forests are the most biologically diverse habitats on the planet, home to over half of the world's estimated 60 million species of plants, animals, and insects. dr. bill laurance: one of the really exciting things about working in tropical rainforests is they're just such a mystery

and there's just so much we don't know about what's here, even just in terms of cataloging the number of species here. right now we think there are somewhere between maybe 5 million and 50 million species living in the tropical rainforests of the world. we are talking about that rough of reckoning here. and one of the reasons that we have such a vague idea of what's here is the rainforest canopy. studies that have been done in trapping insects in the canopy have found in many cases that 80% or 90% of the species that they are finding up here are new to science have never before been documented. and if we extrapolate from what we are finding here throughout the tropical world, we are getting numbers like 50 million, which is just an extraordinary number. so this is one of the last great biological frontiers is the rainforest canopy. narrator: and the heart and soul of these forests are the trees. dr. bill laurance: trees are the foundation of the forest. they form the architecture of the forest. they determine its micro-climate. they are the food sources of most things out there.

so if you change the tree communities you are really changing the ecology and the habitat for just about everything else. narrator: one way that rainforest tree communities have been changed is through outright destruction or habitat loss. this destruction has broken large rainforests up into many smaller habitat fragments. laurance is studying the effects of this forest fragmentation. dr. bill laurance: fragmentation in forest edges affect the rainforest in all kinds of ways. the rainforest under its normal conditions, is a humid and dark and windless kind of environment. it's been surviving, existing for millions of years. and so many, many species have become specialized for these very unique micro-climatic conditions. and then you juxtapose that with a harsh, dry, windy cattle pasture and so the conditions are just completely different. narrator: at the forest edge where these two different environments meet, common plant species that are well adapted to the sunny and dry conditions start to take over

affecting the overall diversity and structure of the forest. dr. sue laurance: one of the important mechanisms that's pushing the change in structure are these vines. what the vines do -- they start to smother trees up near the edge and actually they can kill these trees. and the thing that we are most concerned about with fragmentation and these sorts of structural changes in the edges is that the edges start to encroach into the fragment itself and the fragment starts to shrink in area. dr. bill laurance: whenever you have an environmental change there's winners and losers. so the vines and other things that like disturbance are doing great. what we are seeing really declining dramatically are the old-growth rainforest-interior specialists. their geographic ranges are collapsing they are becoming much less abundant and they are becoming much more vulnerable to extinction. these are the things that we are really worried about. narrator: as you walk in from the edge of the forest, the difference in e environment becomes

obvious. dr. sue laurance: it's a lot darker in here. we are a couple hundred yards from the forest edge now and you can see just what a dramatic change it's been -- a lot cooler, a lot darker. you gothese big forest palm trees, and the forest understory is just generally a t sparser now. we don't have that profusion of vines, and we have got a lot of these sde-loving plants which can't survive on the harsh forest edge. we call thisnvironment in here the core of t habitatragment. and we are very coerned about how much area ore habitat do we have? and what we are really saying is how much area of pristine rainforest is left with aorest fragment? and this is very important to tell what species are going to survive in forest fragments. is the core habitat big enough to have more than one individual of this palm species? because some of these species can be very rare --

there could only be one per acre. so do you need to have 50 acres to have 50 individuals? and will that be enough for that population to survive for couple hundred years? narrator: to discover exactly what the effects of fragmentation are on the rare old-growth tree species in the amazon forest the research team compares plots along forest fragment edges to plots within pristine forest ars. . bill laurance: we have bn studying about 65,000 trees for the last 27 years. and overall that's about 1,300 different species of trees. that, just to put it into perspective is about twice as many scies as occur in all of north america. narrator: by identifying the species and measuring the diameter of the tree, the team can calculate its biomass. once this is done to all the trees then the total biomass of the plot can be determined.

dr. bill laurance: it's an enormous challenge. it really is one of the great challenges is trying to document what is simply out there. and it's tough. i mean, there's no simple, magical answer for that. it takes muddy-kneed forest biologists to go out there with their various techniques and try to count and capture things. and it's a very slow painstaking process. we have teams of field technicians that go out and actually climb the trees. and they collect flowers and leaves that use to help identify the species. we measure the trees. we study how fast they are dyi which new species of trees are coming into our plots. narrator: the researchers found that plots within 100 meters of the forest's edge lost up to 36% of their biomass of old-growth tree species within the first 10 to 17 years of fragmentation. plots past 100 meters exhibited no significant changes in biomass

over that same time period. dr. bill laurance: our fragmentation study of the amazon is a long-term study because things take time to change. they don't instantly disappe. many of the trees would normally live between 400 ars and maybe 1,500 year what perhaps is most stunning is that we are seeing the mortality rates are just going through the ceiling as a consequence of these edge effects and these environmental changes that we are seeing associated with forest fragmentation. so it's obvious that the ecology of the rainforest is just being altered in such a profound way by forest fragmentation. narrator: and it's not just the trees that are affected, but also the wildlife. sue laurance studies the impact of fragmention bird specie dr. sue laurance: birds are very interesting to study the effects of fragmentation -- particularly just the effects of roads because they are highly mobile. they can fly. so a small road of 50 yards or a small clearing really shouldn't inhibit an animal that can fly much greater distances inside the forest.

so i caught birds and put little radio receivers on them and moved them across these gaps to see if they can return to what was their home range of their territory. and they know where their home range is because i generally move the male. and the female will be there calling and the male's returning the call. so they know where home is. but they are just not choosing to cross the road at all. and that's a real concern when you can see that some of the clearing patterns that we have seen in the amazon where they have just got long roads could still leave 70% of the forest intact but populations could still be divided by a very small clearing. dr. bill laurance: the roads are in some sense acting as a sort of a pandora's box. it's oftentimes the first step in this cascade of uncontrolled activities. in the amazon, for example we see roads penetrating into the rainforest. the government is putting in many new roads. and then oftentimes you get slash-and-burn farmers and cattle ranchers and loggers coming in when the roads are there.

you get land speculation. you get a very destructive process which oftentimes leads to just large-scale, wholesale forest destruction. narrator: by providing concrete examples like how a small road can disrupt the stability t rnft, laurance's research is showing just how vulnerable this very fragile, diverse and utterly unique environment really change. dr. bill laurance: but i think we have to be very vigilan it's absolutely essential to understand for the fate of tropical biodiversity what species are gonna be able to persist and which ones are not going to be able to survive in these fragments of forest. narrator: coral reefs have been called the rainforests of the sea. and like the rainforests they are a rich and precious natural resource. but they, too, are being impacted by human action. one small example of this impact

took place in april 1986 when a major oil spill on the coast of panama polluted an area of coral reefs, mangrove forests, and grass beds, including a biological reserve being studied by the smithsonian tropical research institute. ecologist jeremy jackson is one of a group of scientists working there hired to study the ecological effects of the spill. dr. jackson: we worked all the way down the coast for something like 50, 60 miles to get to places that were less and less affected by the spill. and so we had what were in effect control reefs that were along the coast, and we were monitoring the condition on the coral reefs and the mangroves and everything here and then further and further and further away from where the spill was. narrator: the results of the study

were not surprising. the area affected by the spill was severely damaged compared to the unaffected or control, areas. but for jackson, it was the findings made in the control areas after the initial study that would be much more alarming. dr. jackson: two years later, almost all the corals died in the control areas and they died for reasons that had nothing to do with the oil spill. they died because of disease because of overgrowth by seaweeds. they died because of bleaching. and so that was, i suppose for me the real wake-up call that there's nothing close to natural out there anymore and that it was just fundamentally important and interesting to try and understand all these different dimensions of degradation. so what i'm really interested in

is how have people changed the ocean? what does it mean not just for the natural world but for us? and what will it provide for us in the future? narrator: to understand the statof the oceans today, jackson uses data from fish surveys conducted worldwide, along with catch records from the fishing industry. but this data does not provide him with all the answers he's looking for. dr. jackson: if you wanted to know what manhattan island was like as a natural ecosystem you wouldn't go to wall street and survey the birds. wall street has changed in the last 500 years. and in the same kind of way, if you want to know what kind of fish there were in the ocean, you can do a scientific survey of fish today,

but it wouldn't tell you anything. some species of fish are extinct, so it would probably be difficult to survey them. narrator: so to put current research in the right context, jackson compares it with historical records and archeological evidence painting as accurate a picture as possible of the oceans before human disturbance. this picture is called a baseline. dr. jackson: the baseline is the way it used to be. but every generation of fisheries' biologists makes a new baseline when they start their career. and so the fisheries' biologists from 30 years ago -- their baseline was maybe 10% of the fisheries' biologists' baseline from the generation before. this is an example of the shifting-baseline syndrome. it's an incredibly important idea. it's the most important idea

about understanding the environment and human impact on the environnt. you cannot understand the problem just by looking at the way the world is now. narrator: so jackson looks to the past. and while he researches all of the human impacts on the ocean like pollution and global warming his focus has been on the effects of overfishing. he has concluded from various sources that the global population of large fish has declined by 90% since 1950. dr. jackson: we know things like that from data from the japanese fishing industry. they have a massive fishing fleet, and they kept very good records. and in the beginning of the japanese fishery, they fished mostly close to home. and then they depleted the fisheries in the western pacific. so they moved into the north atlantic

and the south atlantic and the central pacific and the indian ocean and all of the different fisheries grounds around the world. and in a period of 25 to 30 years, in the entire global ocean the catch was depleted from 10 fish per 100 hooks to one fish per 100 hooks. that's 90% of all the big fish are gone. narrator: but to jackson this study also falls victim to the shifting-baseline syndrome. dr. jackson: their baseline was 1950. and you can imagine how many big fish disappeared before 1950. so, another way we know about the magnitude of the fish we've lost -- there's this global fisheries data that were essential commercial fisheries' data and they made maps of how much fish was taken out of the northern atlantic in 1900 and today.

and the red color meant that there was lots of fish, and white color meant there were no fish. and in 1900, all along the east coast of the united states and western europe is red. and in 2000, it's white. it's just virtually the richest fishing grounds in the world are gone. narrator: besides the obvious concern of extinction to many of these large fish species jackson asks what effect their absence has on the health of the ocean as an ecosystem. of chief concern are coral reefs. dr. ckson: the important question is how is the functional diversity of reefs changed whether the species have gone extinct or not? is it a complex system that works in the kind of way that supports the healthy populations of fish? is it a healthy system that protects the coastline

from hurricanes and other severe storms? does it perform all those kinds of things? there's no doubt that in that kind of functional-diversity sense, coral reefs have been very, very badly impacted. narrator: like the trees of the forest coral reefs are the foundation for much of the life in the ocean. they provide food and shelter for many plants and smaller organisms which are the bottom link of the food chain. these smaller organisms are the food source for small fish which in turn are the food source for the larger fish that eat them. the simple way to understand it is big fish eat little fish. and the big question is when you remove the things at the top do the next level down just take over? or is the balance disturbed in some kind of way

that it's not that simple? it's pretty clear that it's not that simple. overfishing removes the most important and abundant consumers in a natural ecosystem. and so fish, of course eat fish but fish also eat seaweed. if they are not there, the seaweed grows 10 times faster, 100 times faster in the corals. it grows over the corals smothers them, and kills them. narrator: the absence of fish that allows for this overgrowth of seaweed and the destruction of the coral is an example of how removing one part of the food web completely changes an ecosystem from one that is healthy and diverse to one that is only attractive to a limited number of organisms. it's what jackson calls the rise of slime. dr. jackson: what i call the rise of slime is the introduction of excessive amounts of nutrients

that allows the microscopic plants in the water and also the seaweeds on the bottom to grow at extraordinarily rapid rates. if it gets out of control, there's far more microscopic plants and seaweeds than the grazers can possibly eat. the stuff just builds up and builds up. it dies before anything eats it. it falls to the bottom. it rots. the process of rotting consumes all the oxygen. so all the animals that normally would be using that oxygen they die because of this rotting of all this excess vegetation. and all you've got is jellyfish at the surface and all these microbes. and so it's an ecosystem which lacks all the kinds of animals we want and has all the kinds of animals we don't want.

and so, of course, the big question is will that happen everywhere? or will it only happen in a few place or will we get smart and figure out how to stop doing that and x it somehow? narrator: some of jackson's research is showing that avoiding the rise of slime is not so complicated. in the summer of 2006, jackson and researchers from the scripps institute of oceanography released results of a study that evaluated the effectiveness of recovery efforts on reef systems. the research team sampled levels of biomass for fish, corals, and algae at 34 coral reef sites in the northwestern caribbean and off the florida keys. the sites ranged from fully protected no-take marine reserves to reefs that had been historically overfished. sites designated as marine reserves larger than 100 square kilometers with no fishing allowed for more than 10 years

have the greatest levels in total fish biomass, including not just top predators, but also herbivorous fish who are important in the food web for reducing algae abundance. dr. jackson: in those places -- surprise, surprise -- you don't kill the fish, the fish come back. and there's lots of fish and lots of big fish. and what's really important is even though it's very complicated and we don't understand all the details, in those places where there's lots of fish there's been a huge reduction in the seaweed. now, the corals haven't come back yet because the corals grow slower. so it's gonna take a long time for corals to come back. and, of course, there are other problems that corals have. but at least half of that story -- the elimination of the large amounts of seaweed -- has now been shown effectively, experimentally, through the mechanism of these protected areas in seeing the reduction in the seaweed.

so, is it too late? i don't think it's too late. but will we be able to go to the beach? will we be able to eat fish? what will it be like? that's really hard. and there's a lot of science there. we know it will be better -- you know if we stop killing fish, there will be more fish. if we stop dumping too much garbage in the ocean, the ocean will be cleaner. and it will be better. but what exactly it will be like and how well we can manage it -- to protect the natural biodiversity and to still have fish to eat and still have clean beaches to go -- that's a harder, you know, and that's what a lot of us are trying to understand.

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