Re: What proportion of the world's plants and animals reside in rain forests?

What proportion of the world's plants and animals reside in rain forests?

Well, that is a rather difficult question to put numbers too.

Let's break it down into simpler parts.  There are many types of 
rainforests all over the world.  I live in New Zealand at the bottom of the 
world, where we also have rainforests.  These, of course, are not the 
tropical rainforest that most people think of, but temperate rainforests.  
The reason they are called rainforests is because they receive an awful lot 
of rain; some places get more than 10 m of rain per year.  That is a 
feature all rainforest share, they get lots of rain.

New Zealand rainforest contain about 2200 flowering plant species.  The 
forest also has 4 species of frog, 2 species of bat (New Zealand only has 
these two species of endemic land mammal, very low numbers indeed), about 
20 species of lizard, say around 30-40 species of bird (though this 
includes introduced birds and doesn't include the 10 or so species that 
have gone extinct in the last 1000 years) several hundred species of snail 
(we don't exactly know how many) and countless insects (we really don't 
know how many).  Moreover, New Zealand is a smallish country (about 270 000 
square kilometers) with a reasonable amount of money to spend on research 
and quite a lot of people have researched our forests.

By comparison, Great Britain, which does not have any rainforest, only has 
1750 flowering plant species species, and Papua New Guinea, which is 
covered with tropical rainforest, has more than 9000 flowering species.  I 
can't give you any ready statistics on animal species but New Zealand is in 
between Britain and Papua New Guinea for those too.

In Papua New Guinea and other tropical rainforest nations, they really 
don't have a clue how many species they actually have.  Often these 
countries are too poor to do much research on their forests.  Not only 
that, but many species only occur in small patches, and if you move to the 
next valley, you will find some completely different species.  A "typical" 
4 square mile patch of tropical rainforest contains up to 1 500 species of 
flowering plant, 750 species of tree, 400 of birds, 150 of butterflies, 125 
of mammals, 100 of reptiles and 50 amphibians.  If you could add up all the 
patches this would add up to a staggering number of plants and animals. 

The figures above really don't include many insects.  In a one hectare 
piece of rainforest canopy in Peru the Smithsonian Institute found more 
than 41 000 species of insect, including 12 000 different kinds of beetle. 
Before this finding it was commonly thought that there were 5 -10 million 
species on earth, now we think it is more likely to be closer to 30 
million.

People think that about 50% of the Earth's species are found in tropical 
rainforests.  But there are many species that we haven't discovered yet, 
and many species that have already gone extinct (often through forest 
clearing) before we could find and describe them.  So how can I give you a 
really good answer to what proportion of the world's plants and animals 
reside in rain forests when 
1) we don't even know how many species live or have lived on the Earth
2) it depends on which rainforest you include.  If you include all the 
rainforest it will be considerably more than 50%

A good reference to read is Environmental Science by Charles Kupchella and 
Margaret Hyland.  Other material I used includes;
The Natural World of New Zealand (an illustrated encyclopedia) by Gerard 
Hutching
The Reed Field Guide to New Zealand Wildlife by Geoff Moon
And the notes from the Make your own Rainforest book