Lecture 2 - Tropical diversity, automated transcript
May 28, 2021
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So in the first lecture of this series of three lectures looking at trouble diversity
and we had look at conservation by geography by geography in general and the ecological
and historical factors that give rise to the distribution of species and the distribution
of biodiversity that we see today on planet Earth. So now we've had a bit of a think
about that. And the fact is behind why biodiversity varies.
Across latitudes when I'm going to have a look at Tropical diversity itself. So
this is the diversity, we get around the poles, why it's special, why there's so
much of it. And some of the factors including a human, as a theme, that goes through
these lectures and a lot of lectures that we have in these courses, human destruction
of that tropical diversity. And so, this is just a map of the different one method
of
Find different biomes around the world, as you remember, from previous lecture and
introductory set of lectures. Biome is just a word for a habitat type really. So
a large Regional type of habitat that you get with particular environmental conditions.
These are slightly different to the zoo, Geographic Realms or the biogeographic
Realms, but they're all kind of mainly referring to the same thing.
In this case, we're looking at the type of vegetation that you get at different
in different areas of the world. So you look at left here we have temperates places
including temperate broadleaf forests and temperate step and then higher latitudes.
We have Tundra and tiger forests and then we have deserts and then the things that
we're particularly interested to hear the things that lie in the tropical regions
and I'll come back the map in a second and have a think about which
Current habitat types, which different biomes occur in the tropics. But why are
the tropics particularly special? And why is the climate of the tropics so much
warmer and wetter than it is at higher latitudes towards the poles? Well, there's
three big reasons for this. The first one is that the sun shines more directly in
the tropics than a higher latitudes. At least on average over the course of a year.
So, this means that per unit area, the tropics received more solar radiation than
the higher latitudes because the sun's rays are sort of. If you imagine them as
sort of linear raised like this. They're intersecting the surface at a more perpendicular
angle so that there's more of them that kind of fit close together as they hit the
surface. So on average, the tropical regions receive more solar radiation than the
polar regions. The thing is that the Earth rotates faster at the equator.
Pulse. So if we think about, if we have a look at this globe here, with the axis
of rotation near the poles, each side in the space of a year because the world is
so much larger. The equator there's if you put a kind of string around the circumference
of the planet there, but string around that would be so much larger than if you
put a string all the way around near the pole to move the same number of degrees
in a year, the polar eat the chocolate.
Agents move a lot faster than the polar regions. And the other thing is that the
vertical Direction so up. So as you would stand on the surface of the Earth, so
perpendicular to the surface is perpendicular to the Earth's axis of rotation at
the equator while the axis of rotation and the vertical are the same at the pole.
So if we ever had a bit this this globe here, if you stop on the earth, you're standing
kind of perpendicular to the axis of rotation.
The pole at their tropical region. Sorry, because the X rotation is pretty much
pole to pole. Where is it? The polio standing parallel to axis of rotation? What
that means in in is that it, we get that that greater speed of rotation in the tropical
regions, but also means that the earth rotation influences, the atmospheric circulation
more strongly
At high latitudes than at low.
And that gives rise to a few things. One is that because these factors clouds and
rain storms in the tropics can occur more spontaneously than there was at higher
latitudes where they are more tightly controlled by larger scale factors in the
atmosphere and this means that often rain is more difficult to forecast in the tropics,
but temperature is generally a lot easier to forecast, because doesn't change that
much. We don't see the seasonal effects that we do in the in the regions of higher
latitude.
So, that's a bit about why it's a bit warmer in the tropics and about why it's warm
all year round, and why rain can be a bit harder to predict. Anything think about
is, why there is so much rainfall in the tropics? And again, we're gonna have a
look at this diagram here. So because generally more solar radiation is hitting
the tropics, then the polar regions and
They're therefore generally warmer air tends to rise in the tropics. So I'm sure
you will know that as air is heated up it, expands it becomes less dense and then
it rises into the atmosphere. So as we can see here, on the right hand side of this
diagram, we get this, the air Rising near the equator,
And then it moves up to a certain level. And then it moves, it gets pushed by are
moving up behind it in the same place and then it moves towards the poles. So it
moves North in the northern hemisphere, its South in the southern hemisphere. If
the Earth didn't rotate, we would just get one big convection current in each pole
in each hemisphere. Sorry with are moving up at the up at the equator moving along
the troposphere, to the pole and then down the pole. However because the Earth does
rotate hasn't put this arrow on here.
Takes the East. It becomes a bit more complicated. So because the Earth is rotating.
We have to take this thing called the Coriolis effect or coriolis Force into account.
And what that is is because the Earth is spinning, the Earth is solid and it's spinning
under a gaseous atmosphere. It causes the the air flows to to move to be deaf deflected.
Basically, because the airflo isn't catch to the surface, everything on Surface
moves.
The Earth because the air that sits on top of it isn't attached. The Earth moves
underneath it and it doesn't get pulled along with it, but it does get deflected.
So as we can see here in the northern hemisphere, as, as air moves up and then down
in these convection cells, it gets the deflected, it doesn't move in one straight
line. So we just think about the Northern Hemisphere for now as the air goes up
at the equator moves northwards,
It gets deflected to the, right? So the the white areas we see here are the winds
that move along the surface. Here, we'll talk about the move, the winds that move
higher up in the atmosphere, so it gets deflected the right. And then as it reaches
about 30 degrees north here it meets cooler air that's coming from the poles. As
it does that it cools. The it calls the two air currents at about 30 degrees. And
then, because they're cooler, they become more dense and they sink towards the surface
of the Earth.
And then so we get a, what this causes is a low pressure Zone around the equator
and a high pressure Zone at 30 degrees. So the are sinking at those degrees makes
the pressure on the surface higher and the are rising at the equator, makes the
pressure there. Lower
And then because we have a low pressure at the Equator, the air that has been sinking
about 30 degrees get sucked back towards the equator getting deflected at the right
because of the Coriolis effect on the way.
And so, because of the mixture of Greater solar radiation at the equator and also
the Coriolis effect, we get these convection cells here which are label on that.
We have the Hadley Cell between Norton, 30 the mid-latitude cell in the Polar cell.
So get your different cells of convection, currents and then different prevailing
wind patterns in each area. This then, the reason I explained all this is because
it explains why the tropics are so wet and then why
A dry region around 30 degrees north and 30 degrees south so the warm air that rises
at the at the equator.
In those lobe in that low pressure region as that area is warm. You get a lot of
effort evaporation of water, both from plants, and from the sea and as it rises
it cools, and in those low pressure areas, rainfall is really common. So that's
why we get lots of rainfall around the equator in these tropical regions. And as
it, moves away from the equator, you continue to get rain the high pressure regions
around 30 degrees. By the time, the air has got there. It may have lost some of
its moisture because of the rain.
And also, in this high pressure zones, we get further evaporation and so around
30 degrees, you don't get much rain. So that's why we have these very dry regions
around 30 degrees, north and south, which is reflected in there in the large Sahara
desert. In large, areas, the Middle East and that's why we get dry regions in those
places. So, this doesn't control all the weather on the world. There's other factors
involved, including mountain, ranges and different things. But this is one of the
reasons what this kind of the main driving force, behind the reason behind,
And why the tropics is so warm and so wet.
I'm so now we've had a better look at the kind of underlying patterns on the line,
driving forces behind that we can have a think about what biomes and what habitat
types, that gives rise to. So, this is where the equator is. And as we can see,
these are the places near the equator, the places where we get a tropical rainforest,
and other tropical types of forest that rely on very high levels of rainfall. So,
South America in the Amazon, we have the Congo Basin in Africa. We have Southeast
Asia.
And then there's other parts of other other parts of the world as well, that have
some rain forest. And some of these tropical forests. We have Northern Australia,
we have the eastern half Madagascar and the Western half of India Western strip
at those two countries. So and the reason we get such high rainfall in those places
is due to are moving off the ocean. So are there is a very, has a lot of moisture
in it and it hits the land, it gets uplifted to some extent.
And then you get rainfall on the a lot of rainfall on the edges of those land masses.
And the reason it's on the opposite side is due to that the wind being deflected
in different directions than all the hemisphere, and southern hemisphere.
And then if you move slightly away from the, from the equator, we get these very
dry areas, roughly around 30 degrees north and 30 degrees. South, these are the
Tropics of cancer and Capricorn. These aren't actually at 30 degrees north and Southeast
around 23 and 1/2 degrees. And the reason these, the definition of these places
is the furthest North and the furthest south that the sun can ever be directly overhead.
Head. And so if we think about some in the northern hemisphere at the summer solstice
which is when the northern hemisphere is most tilted towards the sun, this is this,
the sun will be directly overhead on the summer solstice, on the traffic Tropic
of Capricorn, Tropic of Cancer. So which is around 23 and 1/2 degrees north. And
the reason it's that number is because the Earth's axis is tilted away from the
vertical at 23 and 1/2 degrees. So the sun is here and the Earth is on its axis
here.
In the summer, the northern hemisphere is tilted towards it. For the Tropic of Cancer
would be right here. And then in the southern hemispheres, summer, the sun is here.
So it's directly above the Tropic of Capricorn here. So that's why they're place
where they are. And these lines are roughly the last dude where the limit of Frost's,
any point. So you don't tend to get Frost's overnights unless you're at high, altitudes
closer to the Equator than these tropical lines and that's very rare.
Avant for what type of plants can grow, because lots of plants will be sensitive
to frost, any kind of freezing kills them. So it's these are all very important
to be kind of ecologies. We get. You can also see that they tend to coincide with
the company's very dry regions that we get because of the high pressure areas where
air is descending back towards the planet.
And then we also have these subtropical regions which where you get some tropical
characteristics but we're moving up towards more temperate regions here.
and this is just showing how
how warm the tropics is. So here we have the sea surface temperatures and this is
the minimum. So, so around the equator there's a minimum is a very high as you move.
Further away, we get a little bit, they can be, they can get a little bit colder
as you see even in these kind of, I think subtropical regions just above those dotted
lines. It doesn't get below 18 degrees so it's still saying very warm the minimum
temperatures you.
Also, controlled not just by last year, but also by other things. So as we can see,
the Indian Ocean and the ocean around australasia, into the Western Pacific, those
tend to stay a bit warmer than the Eastern Pacific and Atlantic, and it's just due
to kind of ocean currents and things like that, and although wet weather patterns
as not so important. But we can talk about here, but it's just worth mentioning.
And this also here, we can look at the the rainfall levels that we get around the
tropics.
Which also can be very high just bear in mind that here when rain falls in centimeters
rather than millimeters. And so these are some very very high rainfall regions where
we get the darker colors here. Blue is just green for in January and red is rainfall
in July. So I think this is where the Region's times a year. We get maximum rainfall
in these regions. The references where these figures came from in the notes on the
under this slide on.
point and then just as these materials were designed for God isn't mine, while we
have a closer look at Asia ecological zones,
So you can see lots of Southeast Asia. So Malaysia Indonesia down here is tropical
rainforest, but they also get some of this that appears up into Mainland southeast
Asia. As we look up into Thailand and Myanmar. And as I mentioned before, we do
get some rain forest on the west coast of India and Sri Lanka due to that warm moist
air moving being
Moving being deflected the right as it moves higher latitudes coming over the land
and then potentially being uplifted cooling down and raining, which gives us High
rainfall on the west coast of India and Sri Lanka. And you that can then support
tropical rainforest.
So it's also worth bearing in mind that it's not all about tropical rainforests
so they're not the only biomes that we get in the tropics and they're all not even
the only Forest. We get in the tropics, actually, we also have tropical moist deciduous
forest and tropical dry forest. And again, these tend to follow that gradient of.
As you get slightly further away from the equator, you get slightly more slightly,
less rain, sorry, so you get slightly different habitat types.
We're going to have a quick look at here.
So there's tropical moist broadleaf Forest. So these tend to be be characterized
by trees that don't lose their leaves. So in the temperate regions, we have lots
of deciduous forest where the trees lose their leaves over the colder months and
we don't tend to get that in the in these types of forest, these characterized by
high levels of rainfall over 2,000 millimetres annually. So that would be over 200.
200 centimeters annually. So, this is just the maximum rainfall. Here we get in
a month. This isn't yearly low variability in annual temperature and says, no Seasons.
Really? Because the equator is always sort of pointing towards the sun, regardless
of which way the Earth is tilted and is also characterized by diptera cops. So these
trees that have these very large buttress roots. That allow them to grow, very tall
and stand up. Even in tropical rain forest soils, which tend to be quite thin.
And so they need these kind of boxes to help them stabilize themselves and also
characterized by extraordinarily High biodiversity. So maybe half of the world's
species just in this biome of the tropics and then as we get further away from the
or even equator slightly less rainfall we get slightly different habitat types.
So there's tropical moist, deciduous forests, also known as Monsoon Forest.
So these places have dry seasons but and have so slightly low, rainfall annually
and they have dry seasons, but they can also be under Monsoon Dynamic. So they can
have periods of year whether it's experience. Extremely high, rainfall. Yeah, the
rainfall tends to be a bit more concentrated in certain parts of the Year. Further
a again when it's a bit dryer we have tropical dry forests. These are long dry seasons.
So deciduous trees predominates, so they can lose their leaves over these dry seasons.
And I've also very sensitive to burning because they are so much drier and then
we have these tropical and subtropical coniferous forests as these attempt to be
found at high altitude. They can also be called cloud forest in some places. So
these Forest have low biodiversity but very high endemism. So the species you find
in those kind of photos, don't tend to occur anywhere else on Earth.
Okay, I'm just a bit of case study. We can think about the hacker carburizing landscape
of Northern Myanmar. There's a very interesting paper that looks at the looks of
this area, which is a reference in this, in the notes for the slide. So, this one,
the last exemplars of large contiguous forests in in this region of the world or
really in any region. The world are still large areas of the Amazon.
And some parts, the Congo that have large continue. Contiguous forests, but getting
kind of undisturbed areas of forest is becoming rarer and rarer, this partly because
access is limited due to both biogeographic regions. So, it's very hard to access
just in terms of it being hilly and also due to political reasons as it lies at
the Confluence of three different countries in an area, where there has been conflict
in the past, it means that there can be political reasons.
So access is also limited. It has some of the highest concentration of endemic species
in the world. So the paper that is reference in this, in a note to this slide shows
that nine vertebrate species, new to science have been described in the last just
over 20 years. So things including this Leaf deer species of catfish and a Babylon,
which is took a bird. So I really recommend you reading this paper, you get the
time because it's really, really interesting.
It's also worth talking about that's as it is an exercise in the conservation series
of lectures. I think for the very last lecture in that series of six, that looks
at conservation in this area and interactions between ngos local people and how
there's been some conflict there. So it's worth tying the kind of biology in the
region and the Ecology of the region which talked about here with the political
side of things, which I briefly mentioned just before
So not all rainforests of the same. So it's not that you get exactly the same vegetation
communities in different parts of the world. So if we see here, we're looking at
Sabaton Borneo. This might be the kind of the more classic Green Forest that you're
thinking about when you, when you talk about rainforest and the one that you often
see on Nature Documentaries.
So yeah, we have to try a different tree, species present in these places. So, the
tree species in Borneo, tend to be a lot taller. And then you can see this kind
of rainforest that occurs in Northwestern, mine Mart, where we don't have these
very, very tall trees that stick out of the canopies and there's slightly less variation
in in height. So, so it doesn't really matter too much about that but it's just
worth bearing in mind that not all rainforests are the same
And whilst you may have a certain picture of that. There are very important, but
pictures and your heads from Nature Documentaries. And things, there are very important
differences and very important habitats that don't look like that, but I still classes
rainforest and still very, very biodiverse. So on that note, there's an interesting
paper that's again cited in the notes for this slide. That looks at African rainforest
and wide, might be different to different places. So this is just a highlight, how
the
This is that we see I'm so that African rainforest. These are the kind of main points
that go out this paper and why they might be difference. So they're relatively dry
and cool. Compared to other major tropical forest regions. There's a relatively
low and plant species, diversity and yet extremely high animal biomass in the non
heavily hunted forests. So this links a little bit to what we're talking about in
the introductory series lectures where we looked at mass or extinctions of large
body species as humans spread
Around the world. So Africa is the only place on Earth it still has a relatively
intact community of large-bodied species, large body of mammals because they didn't
really go extinct or they weren't necessarily hunted to extinction by humans. Possibly
due to several reasons including the long coexistence of early humans with these
species that they adapted to the presence of humans. So this might be another. That
would be another potential reason why we see this.
We get this extremely high animal biomass, but it's not just biological differences.
There's also social differences, political differences. So it's complex patterns
of customer in state land, tenure built-in long, histories of low-level Forest exploitation.
And there's a dominance of selective logging small-scale farming bushmeat hunting
as the major forms of pressure on the rainforest biome in contrast to the agro-industrial
pressures, the dominant tropical Americas and Asia. So this means that the human
pressures on rainforests are slightly different in Africa, to in Southeast Asia,
and in South America.
So, whilst you may get more industrial logging in Southeast Asia and in and in the
Amazon. So, we're getting large, kind of whole-scale clearance of the landscape
in Africa, partly due to these kind of patterns of customer in line State tenure,
I was, I just mentioned you don't tend to get that kind of industrial. Deforestation
said you get selective logging. So people going out on a smaller scale and picking
valuable trees to cut down yet, smaller scale, farming and you also get bushmeat
hunting.
So what this means is why we don't potentially get the large clearance of large
areas of forest, we do get this thing called deformation. Where even though the
habitat is still there, the abundance of animals and their population numbers do
go down partly due to the bushmeat hunting another at these kind of potentially
lower level or less industrial pressures. And but it's all very important. And if
they'll cause large declines, all of these,
Of those animal populations. The other thing to think about is the particular context
of mineral and oil driven economies of central Africa.
So, there's lots of oil reserves and lots of mineral reserves under areas of the
Congo Basin, and because people are making money that way or Industries are making
money by mining. We get Lola. We get relatively low levels of deforestation agricultural
activity.
So, so again, it's kind of contracts why we're not seeing this Industrial Level
deforestation in in Africa. This does definitely come with its own problems with
looked small-scale mining. You tend to get lots of mercury poisoning, and lots of
heavy metal pollution and things like that, which it also causes huge problem for
biodiversity and, but we did. We have see slightly different patterns of human pressures.
We don't get as I keep saying this kind of whole scale, agricultural Industrial.
Deforestation and there are definitely problems with the Central African rainforests
in Social and biodiversity terms. And one of these is the poverty and long, poverty
challenges and also the long history of conflict that you have in some of those
Central African countries. And so it's just worth looking at the differences between
these rainforests. So, not all rainforest to the same, both from a ecological biological
and biogeographic point of view. But also from a political point,
Entity.
We talked about previously a little bit. Not, all tropical, ecosystems are rainforests.
We also have tropical savannas and dry forests. So we talked a little bit about
the dry forest earlier on, but it's also worth thinking about the about Savannah's.
So we have as you get as we talked about before, as you get a little bit further
away from the equator, we have less less rainfall, and therefore, we get
Biomes aren't dominated by the rainforest trees that we see in rainforests. So savannas
are defined as ecosystems that are where you get a mixture of grasses and trees
to varying, in varying proportions that can be. You can get standards that are very
tree dominated. And you can get savannas are very grass dominated, but their biomes
that are that exhibit, a mixture of trees and grasses to varying extents.
And those are things. Can also vary in the same place over time as the environment
changes as more or less rainfall as you get droughts over several years. So if you
think about kind of the classic idea of an African savanna that you see on Nature
Documentaries and things will time, so why Jerry is a grassland? Also patches of
acacia trees and other trees that are present in the landscape and then grassland
is quite self-explanatory. That's easy systems that are dominated by grasses and
have very few or no.
Oh trees.
I'm suspicious mentioning the. Let me talk about tropical ecosystems. Yes, tropical
rainforests are incredibly important and very important from a conservation. Point
of view. We don't get we can't forget these other items as well, these dry forest
and also these tropical savannas
So, as we say here, large areas of Savannah and small areas of dry forest dominate,
the global Tropics outside those regions where rainfall is high enough to support
rainforests. And again, there's this assumption that the rainforest is the biome
riches and species in the tropics. And I'm not arguing, that's not the case. But
we definitely have to think about how many these other slightly drier ecosystems
that I'm still very very by diverse until very important for conservation.
So as we see here, there's some looking at some of these species estimates and offer
dry forest and Latin American and Caribbean looking at Savannah's in central Brazil
and also these places are are also have been under great threat. So it's not just
rain forest where deforestation occurs as we see here, our cultural expansion in
dry forest and Savannah areas in Latin. America is vital for conservation, especially
given that they've already suffered far, greater deforestation Amazonia.
So in proportion to their size 3 for deforestation and dry forests has a much greater
proportion of the dry forests. In South America have disappeared than the proportion
of Amazon. The Amazon has been deforested the Amazon rainforest. So the Amazon rainforest,
a much bigger. So, a much smaller proportion of that total rainforest has been destroyed
than the news dry forest with where almost all of them have disappeared.
So these are just some pictures of these different different tropical biomes that
we can get here. So the reference to this, again, reference in the notes. So it's
worth having a look at this paper. And just seeing that it's a tropical it's just
a highlight that tropical biomes that contain a lot of biodiversity and not all
rainforest. There are these different types as well that are very important and
just to kind of highlight this. So have a look at the Brazilian Atlantic Forest.
so this is one of the largest rainforest of the Americas originally coming around
a hundred and fifty million hectares, which is this
Which is this region of Brazil here, some kind of south east coast. And so once
it's called rainforest here, according to our definition that we had earlier, not
all of it is, is actually classes rainforest because as the even though the
The coastal areas receive large amounts of rain year-round reaching more than four
thousand millimeters in and Forest received much less around a thousand millimeters
per year. So, if we go back to our mission of a rainforest earlier, on, for a tropical,
moist broadleaf Forest, we have to get greater than 2,000 millimetres and then we
have these different different biomes that occur with less rainfall at different
altitudes. So I'm gonna wait,
So, so it means that those kind of Inland for us, don't come into that class all
the tropical broadleaf Forest Rain Forest which we had before. So this, this variation
of rainfall and also a large altitude and range her favorite High, diversity and
end endemism. That means that because we have these very, very different environmental
conditions over a short
Over short distances over a small spatial range. And that's favored speciation and
the production of high diversity and also because we have kind of Rapid speciation
those species, haven't had the opportunity to disperse very far. So we also have
high endemism they're not found in many other places.
As this give rise to these very high numbers of species, over 20,000, species of
plants, and all these different numbers of species have different different taxa
as well. And but the slightly worrying thing about this is that even though this
has been a very by diverse region its experience really really high deforestation
rates much higher than the kind of deep Amazon and other Western result that we
think about as the kind of classic rainforest.
This experience really high amounts of deforestation and putting a lot of these
species under threat because there's just very little of this habitat left.
And so if you want to know a bit more about that, again, reference in the notes
to the slide. So we've had a little look at the kind of forest types and the other
habitat types. Do you get in the tropics or about their conservation. So these are
the kind of the main threats that these tropical biomes face. So we've talked a
lot about deforestation which is kind of just a forest way for my habitat loss really.
So we're not cleared for agriculture, whether or not it's cleared for Timber.
All these other things. And so this also includes verified, it's not just people
going out and cutting trees, these can be forest fires, so they can be not caused
by humans, but also they can be caused by humans on purpose, which we'll talk about
in a particular type of rainforest. And for a while, climate change to, this is
especially the problems for problematic for how's Jude species, which we talked
about in the conservation set of lectures and also Coral. So it's not all about
Terrestrial biomes here. Also think about Marine places. So climate change is leading
to this thing called Coral bleaching where corals are is symbiotic. The colors that
you see underwater are the result of a symbiosis between corals which are animals.
And is thing called, as you unfairly, which are a special type of algae that live
with the coral, both in size, and there's an exchange their of energy and and
Nutrients. When there's enormously high temperatures, these corals get stressed
and they can expel those expel, those Plankton there's algae sorry so that they
corals then die and they also lose their color because that that those algae won't
give the call its color and you also get synergies with diseases. So are these is
the environmental change making it easier for diseases to spread?
Through populations. This is also that also links as well with deforestation. So
as we get more and more access to these Forest regions, are we taking diseases in
with us, which then are we transporting diseases around that then affect tropical
species. So a really important example of tropical disease spread, that's important
for conservation is the kit. Rid fungus, the cause kit Trio mycosis, in Lots amphibians,
which is a fungus that infects their skin and can
Can cause death very quickly but it also disease can jump the other way. So, these
evidence now that links the destruction of the natural world with higher rates of
zoonotic diseases. So diseases that jump from animals to humans, which is becoming
more and more important in light of the covid-19. Pandemic there's also hunting
for bush meat and valuable body parts for the illegal Wildlife trade. So bush meat
is just a kind of a word for
For hunted wild and animals so animals that people go out to eat, go out to hunt
for food, so that's just, it's just another word for that, really?
This is quite prevalent in certain areas the world. So western Africa as you talked
about this quite betrayed and that southeast Asia as well in certain areas and you
know, a lot of people rely on this for import as important source of food and important
source of protein. But the challenge lies in trying to do that in a sustainable
way.
Again it's very easy as a western person to point fingers and say or you shouldn't
be going on the forest to eat these animals. But you know, if it's one of very few
sources of food then it becomes quite hypocritical and not a helpful or constructive
way to to try and solve these problems.
And then one side that we look at valuable body parts for the illegal Wildlife trade
introductory series of lectures. I talked about pangolins which I used their scales
are used in traditional Chinese introduce traditional East Asian medicine. So there's
that's just an example of this so there can be animals that have particularly valuable
body parts. So tiger bones as well. Using similar way, a rhino horn is acutally
example, but they don't really a cone rainforest. It's just a different example
from Savannah, biomes.
And then this hunting and poaching is facilitated by deforestation which reduces
dispersal and facilitates greater access into the forest by the creation of logging
roads and logging Trails. So people can get further into the forest to hunt for
these animals. And finally we have a look at the invasive. We can think about invasive
species. So an example of how this has affected tropical biome is the introduction
of the brown tree. Snake on to Guam which is a island in the Pacific where this
tree snake was
Was introduced, but the birds that live there didn't have adaptations to deal with
a reptilian Predator. So these Brown tree snakes kind of went a bit rampant and
a lot of the endemic bird species on the island. I don't have adults or eggs or
young, and it has led to the extinction of quite a few species and the decline of
others to. That's a good interest. In case study, if you fancy looking it up,
As we have a look at deforestation, it's been going on kind of in areas all around
the world for a long time and decided it might be a little bit difficult to see.
We can see that the highest rates of deforestation, which are their kind of the
green and Red's. Here are concentrated in in Southeast Asia, mostly. So as we talked
about there are differences between the threats that face different rainforests.
So there has been deforestation in in the rainforests of central Africa. But we
getting much higher rates in the edges.
Amazon in South America. So they kind of South Eastern edge of that rain forest.
And also in Southeast Asia, where lots of deforestation is happening to clear room
for oil palm plantations and a lot of culture. And this is just a comparison of
of different of deforestation as occurred in, in comparison to actual tree cover.
So we can get the tree cover is much higher in.
In these tropical region. So in South America, in Central Africa, and in South East
Asia, this is the period of 2000 to 2012. And so there's three different colors
here, as well. As the tree cover, we have lost in red, we have gained in blue and
we also have this pink color here which is places that experience a forest loss
and then a subsequent Forest game. So whether they were cleared for short, so mad
culture, or trade, cleared for Timber and then the forest
How to regrow, which is what we get in magenta here. So we can see that in areas
of America. So near Florida, and the southeast of the USA. We've had kind of forest
have been cleared and then allowed to regrow. So whilst that is is good because
the forest is coming back. If we think about, we had a quick look in the introductory
lectures and the it also comes up in the conservation lectures but the difference
in conservation value or diversity value of primary versus secondary.
Rest. So when we do go from primary to secondary Forest whilst we you still have
that habitat structure. You do lose quite a lot of species so it's whilst there
maybe for us in those places. It may not be as valuable for biodiversity as it was
previously. So again we can just see that there's Forest loss going on in in rainforest
areas around the world and it's worth noting that a lot of kind of Southeast Asia
here is in Pink. So Forest has been cleared and allowed to regrow potentially
And but as I just said, it may be that lots of those places that now secondary Forest
isn't as valuable to but for biodiversity as it was previously and we may have lost
or extirpate a lot of species in those areas. They are just looking at the
Kind of the figures behind that work again, cited in the, in the notes of this slide.
So, Global Forest loss, Global Forest game. So, there's a kind of a net loss of
forests, quite big, net loss between 2000 and 2012 for its losses, accelerating
the tropics and also whilst there's been some successes. So Brazil up until a few
years ago was doing very well, reducing deforestation that has changed a bit in
the last few years due to political reasons but
The nose kind of production. Deforestation were offset by increasing Forest loss
elsewhere. So whilst there have been wins in the past. Again, those winds are sort
of have been undermined and past few years in Brazil and deforestation has been
accelerating in Brazil. Again, the last few years,
they can be offset by by increases in deforestation rates elsewhere.
I'm just have a quick look at the tropical peat, swamp forests. So their deforestation
isn't just important for biodiversity. You can use also lose other ecosystem services.
So the areas in Black here are areas of this tropical peat, swamp Forest. So these
are our forests that lie on Pete.
And here we go.
Where Peter is a type of soil that's formed by the partial decomposition of organic
matter in acidic conditions. So you don't get a total breakdown into soil. You get
this thing called Pete and that locks in a lot of carbon. So it's really important
for preventing climate change that we that we keep that pit in the ground. Really?
So these are Forest tropical forest, that grow on this on, Petes on this partially,
decomposed organic matter. So Indonesia holds the largest amount of tropical peacock
Globally. And it's releasing. Lots and lots of
CO2 as it's drained and d4d forested and drained. So the way you kind of destroyed
Pete, if you want to is to drain it because it's very wet and that's part of the
reason that it doesn't decompose because you get these acidic wet conditions, that
means it is difficult for the organic matter to decompose. So by draining, it allows
that decomposition to happen and it releases a lot of CO2 in the atmosphere.
So these forests have been recently logged, a drained logs but also drained burning
converted for agricultural purposes. And when they, when they are, when they have
been dry, they're also very prone to fires especially in dry El, Nino periods. When
there isn't much rain, in this area of the world, and these fires can be set on
purpose to try and Aid the clearance process. So, the quickest way to try and clear
an area of agriculture in this kind of ecosystem is too.
Is that either partially DeForest and then try and burn the Pete's when it's dry
enough to do so. So in drought region in the wet Seasons, it's probably not dry
enough to burn really, but in very dry seasons, and very dry times. You can kind
of set the place on fire and it will burn for a long period of time. It's not only
a problem for greenhouse gas emissions and biodiversity because we losing habitat
in that way. It also causes really serious smoke that blows over into other countries
and can cause political tensions and health problems for humans as well.
Yes, and it's also it's releasing huge amounts of carbon dioxide. There's some estimates
that place as much as 3% of global total Global anthropogenic emissions, which is
a huge amount and it's is important for climate change, but also for biodiversity
as particular, this paper against isil in the notes, I found that for freshwater
fish. So up to around over 30% of freshwater fish in this area of the world.
Found in this peat swamp. Forests on Peninsular Malaysia and then there's also High
rates of species richness for the other taxa in on Borneo as well. So it's just
worth. This is just a kind of a case study of why certain habitat types are important
for biodiversity and also for other ecosystem services.
So yeah, southeast Asia, Southeast Asian forests or some of those threatened in
the world or are the most threatened in the world. So the data we looked at before
was kind of 2000 to 2012, it may be that deforestation rates are really stepped
up since then. And we can see these pink areas here.
Up areas where there's been really, really high rates of deforestation. And lots
of this is due to, especially on on the islands of Malaysia and Indonesia and Sumatra
and Borneo are due to clearance for oil palm plantations because all the partners
extraordinary lucrative at the moment. So, yes, that's just kind of looking at how
it's not just Malaysia and Indonesia as well, where we get this kind of Deep Purple.
There's also been quite a lot of deforestation.
Ation on Mainland on the mainland as well. So Cambodia, Vietnam, Thailand, Lao might
not. We're getting quite a lot of deforestation there. It's just that it's mostly
concentrate. At the moment in Indonesia Malaysia.
The problem with this is that southeast Asia overlaps with, for biodiversity hotspots,
there's four here because there they have slightly different fauna which links into
the fauna and Flora. Sorry, they exhibit different species which links into the
biogeography lecture. And so The Wallace Line runs here, just east of Borneo and
west of sulawesi. And that's the one that separates the, the form of
Chef on the kind of australasian type fauna that we get to the east of that line.
So we have kind of for biodiversity hotspots here that exhibit slightly different
species compositions, but all very, very important for conservation. So if we're
losing place, the forest in these places were getting a lot of habitat loss and
it's gonna be really important for Global conservation because of these biodiversity
hotspots which have extraordinarily High rates of endemism. So this means the percentage
of endemism here means the percentage of species of each of these taxa that occur
only in
These hot spots are not outside of them. So as we can see, say, we clear. All of
the, all of the forests in this Sunderland hotspot here, 80%, almost 80% of the
amphibian species that don't occur anywhere else. So if they go extinct there, they're
extinct everywhere forever. So that's why the loss of these Southeast Asian for
us is really important for conservation.
And just to highlight how important that is we can look at biodiversity loss in
Singapore. So as Singapore is a sort of a very small country. A lot of it is City
experienced very high rates of habitat loss so over 95% of its forest was lost over
a hundred eighty three years and if we can if we look at the rates of extinctions
in Singapore with this very high level of
Habitat loss. So as we can see here, these are different types of groups. And we
have the gray bars are recorded extinctions, then the percentage of species that
gone extinct in Singapore in each taxa. And then inferred, which is species that
necessarily haven't been recorded, is going extinct because we either never recorded
them at species or because they, there is enough evidence to say the definitely
disappeared. We can further, you know, a lots of these up to over a sense of fish.
75% of mammals and we can kind of work out have probably gone extinct in Singapore
due to this mass amount of habitat loss. So if we extrapolate that out to the whole
of Southeast Asia using a calibrated species area model, so this will imply that
the current unprecedented rate of habitat. Destruction in Southeast Asia will result
in the loss of 13 to 42% of regional populations over the next Century. So so what
this work is doing is it's taking
In the relationship between habitat loss and extinctions in Singapore and it's extrapolate
that over southeast. Asia. Again, reference the notes of this slide and not only
will be species go extinct from this region around, half of these are will be endemic
that region, which means that if they go extinct, there they go, extinct globally.
So southeast Asia is extraordinarily important and one of the frontiers of conservation
a moment, because of this habit,
Lost because of deforestation because the extremely high levels of diversity and
that will be lost because of that.
And so we're just gonna have a look at an example from my online. Now. So again,
this is just kind of highlighting the point of how much Forest has been lost in
Southeast Asia over the last 50. 52. Looking at here are what some of these go back
to 1900. So kind of over the 20th century, we're losing extraordinarily, large amounts
of forest, and it's quite harrowing to think about how many species have been lost
because of this
So it was gonna use myanmar's a keystone now for thinking about why this deforestation
is occurring so this is the different habitat types in my own Mar here and there's
an exercise looking with some of these maps in the conservation series of lectures
where we looking at protected area design in that one. But these maps are just from
that exercise. If you want to look closer, look at them.
And this is the areas where you get Forest cover art recover in myanmar's. So generally
around the edges of the country rather than the middle, which is more loan lenders,
very suitable for farming. So this just have a look at where forests occur.
I'm going to be compared, that's the the rate of the
Tri color or the amount of tree cover on the left hand side here. So again we can
see that it's very high cut around the edges of my mom with the rates of deforestation
which have been quite high in the Eastern provinces of cushion and Shan States.
But I've been highest actually around the coasts and what this and that is partly
because of the the high population densities there of humans.
And the forest have been kind of being disappeared in those regions are normal kind
of rain forest types that we talked about, but also Monsoon. Sorry, not want. Seems
also Mangrove forests. And as we talked about a little bit in the introductory series
of lectures, they're extremely important for Coastal protection from extreme weather
events and other ecosystem Services. They provide so the loss of those Forest is
extremely important. But the here
The so whilst the amount of tree cover is biogeographic the the is controlled by
Geographic factors. The amount. Deforestation is largely controlled by social and
economic factors. So again, we have to think about how those things interact. When
we think about conservation, it's not just about one of the other, it's about how
they go together. And this paper, which again, is like the notes gives provides
a kind of a causal Network, for why this
Deforestation is occurring, the numbers. Here, it looked at it, ask people to report
basically why they were seeing deforestation around the country. And so the numbers
here are the number of responses that cited each of these things. And we can see
that not summer. So some of the deforestation and degradation Forest degradation,
we're getting is due to subsistence. So that means people trying to make a living
for themselves and their families. So if their subsistence farming, they're growing
their own food.
They're going out to cut trees for fuel, is this Fuel and charcoal production? And
also these non-timber Forest Products which isn't causing deforestation but is causing
degradation. However, the more important aspect here is the commercial deep, the
commercial destruction of these habitats. And so we're looking at here, we're looking
at kind of commercial, logging mining, these other things and what this paper does
is it just it delves into a little bit about the kind of complex social and economic
caused causation of deforestation.
My mom so it's not easy to say all will go to these people who subsistence farming
and we need to tell them to stop because there's other reasons for the deforestation
as well. And doing this kind of work and working out, what's causing this habitat.
Destruction is extremely important for conservation because we can't go out and
stop it if we don't know what's causing it. So I really recommend that you read
the paper and some really interesting work.
Okay great, thanks so much for listening. That's the so that that limit Al paper.
At the end, there is one that was just talking about with this causal Network. So
thanks for listening. There's just one more lecture in the series and yeah, that's
alumina. Thanks.