afternoon thunderstorms caused by local instability and the precipitation is copi-
ous. In some places, precipitation can average upwards of 800 cm (314 in) per
year. Plant growth is prolific and represents the greatest diversity and yearly bio-
mass additions on the planet. The forest is quite complex with hundreds of tree
species per hectare. The tallest trees sometimes exceed 50 m with several other
canopy layers resulting in a perpetual dimness on the rainforest floor.
Boundaries
Boundaries are lines that separate space into defined, discrete units. They may be
tangible or imaginary, may be visible uponthe landscape or exist quite literally
in thin air, and may appear at any scale, from a few inches or centimeters in length
to many thousands of miles. In many instances, boundaries are not actually lines,
but function in two dimensions as a plane, because the division marked by the
boundary extends below the surface of the earth and into theatmosphereabove
the boundary marker. Boundaries are set by humans, and many other species,
and can be associated with plant life as well. They can be naturally occurring
features, or may be constructed or imposed by individuals or groups. Boundaries
are frequently established due toterritoriality, the human or animal desire to con-
trol a given space. Often boundaries are absolute and rigid, as in the case of an
international border, but they may also be gradual and porous, as are the bounda-
ries dividing the various dialects of a language, for example. A boundary may be
created to enclose a location to identify it, or its purpose may be to prevent some
exterior force or element from entering a specific space.
The concept of a boundary for human society has probably been in place since
well before the dawn of civilization. Most people have a subconscious sense of a
personal boundary, enclosing a personal space. Unauthorized or unexpected intru-
sions across this division into one’s personal zone typically lead to feelings of dis-
comfort, anxiety, fear, or aggression, depending on the type of incursion and who
is violating the boundary. The precise location of the personal line differs from
society to society, and often between genders, but represents perhaps the most fun-
damental boundary that guides human relations, even if many are not fully aware
that such a line of defense surrounds them. Other boundaries are more overt and
obvious. Some boundaries may function asbuffer zones, which serve to separate
two actual or potential adversaries. A demilitarized zone, such as that which exists
between North and South Korea, is a good example. A type of boundary that most
people have encountered in some form is a border. These lines of division operate
on many scales. Borders are established to legally demarcate jurisdiction over a
Boundaries 37