Canopy research
One important reason why there are scientists doing research in forest canopies
simply is human curiosity combined with the fact that the largest part of the
ecosystem forest, the canopy, is not or only heavily accessible. This unattainability
led to the impulse to explore the unknown. One can compare this with the interest
in deep sea or space research. During their journey through South- and Middle
America, the German Alexander von Humboldt and his French compagnion Aimé Bonpland
already observed that there are different life forms occuring exclusively in
the canopy of tropical trees and forests. They collected various epiphytic
orchids or bromeliads from fallen trees. On the picture you can see an epiphytic
bromeliad lying on the table.
The intense and systematic exploration of forest canopies did not begin until
the end of the last decade. The main reasons were the bad accessibility of
tree crowns and often the ignorance of biologists. Only ornithologists raised
their eyes occasionaly and foresters and plant hunters climed trees drudgingly
to collect fruits and seeds. The starting shot of modern canopy research not
surprisingly fell in the tropics, where biodiversity in general and that of
canopies in particular is highest.
In the 1970s and 80s, pioneers of canopy research like Nalini
M. Nadkarni ( ),
Margaret D. Lowman
() Donald
Perry or Andrew W. Mitchell used modified alpine rope techniques to climb almost
every tree of interest. In the following they constructed small platforms around
trunks of tropical tree giants. Later, bridges, walkways, aerial tramways and
even dirigibles were built and altered to study the canopy as intense as possible.
Perry was the first who saw a vertical stratification of insects (forest dwelling
bees). Until now, this phenomenon was observed many times and led to the general
rule that several zones of different organismical composition exist in forests
between ground level and the highest canopy layer. Later, Perry erected an aerial
railway through the canopy of a rainforest in Costa
Rica ().
This ecotouristical project was copied several times and rendered immense revenues.
In the year 1982 the north american entomologist Terry Erwin shocked scientific
community with spectacular results of the number of insects and spiders occuring
in the canopy of one tropical tree species. Using a fogging maschine he blew
an insecticide into the tree crowns and collected every insect and spider that
came off. He could identify for instance 1200 beetle species from this tree
species of which 162 were restricted to this particular plant. On one tropical
tree he detected more ant species than are known from Europe. He repeated his
studies in other tropical countries and received comparative results. These
and other findings started an excited discussion about global diversity of
organisms (biodiversity) with the important result that global biodiversity
had to be adjusted. Global biodiveristy was estimated 1.2 millions different
species world-wide prior to Erwin’s investigations. Nowadays global biodiversity
is estimated to 5 to 10 millions species, with extreme values reaching 30 millions!
About 40% of the land living species (plants and animals) are predicted to
be canopy specialist. That means that they occur only in the canopy and rarely
if at all descend to the forest floor. We can also predict that the majority
of this species will never meet human’s eyes because their natural habitat
disappears rapidly or is commuted into monotone plantations.
For the end of the 1980’s the spectacular flights of the french botanist Francis
Hallé with his colourful hot-air dirigible attracted public attention
().
Hallé and his team started their first expeditions above the untouched
rain forests of French Guiana followed by research projects in Gabun and Madagascar.
Besides his studies on biology, ecology and structure of rain forest trees, lianas
and epiphytes his interests were directed towards bioactive compounts produced
by plants. He could discover for instance that their production in the canopy
was significantly higher than in shaded and deeper areas. The dirigible currently
is in use for the joint research project IBISCA
().
Since 1990 construction tower cranes, normally used on building lots, were used
for canopy research purposes. For further information follow this link Canopy
Cranes world-wide().
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