scars and smoke plumes result from biomass burning in
the savannahs of the southern Democratic Republic Congo.
This image was photographed during Expedition Four.
Space Chronicles #16
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ISS Science Officer Don Pettit
and the Production of Food
gives us clues on how to do things if we are only willing to listen.
After observing the jungles of South America and of Africa from
orbit, one notices how dark the landscape appears. Jungles are about
the darkest land features you can observe in full sunlight. They
are so dark you need to open your camera lens a stop and a half
to obtain an exposure that shows any detail. If there are thin clouds
masking part of your view, you are fooled into thinking you are
over the ocean. When you notice rivers with braided channels and
meandering loops of chocolate brown, onlythen do you realize that
it is jungle and not water.
of abundant jungle life seem to suck up every photon that falls
into the area. This is exactly how things should be if you want
to efficiently use light for photosynthesis. Any ray of light that
escapes the jungles is lost energy for growth, hence, life. And
we all know how hard life is in the jungle.
When you pass
over farmland, rich with vibrant crops, you see something different.
Farmland is bright, much brighter than the jungles. You need to
close down your lens by perhaps two stops to obtain similar film
densities. This is a factor of four. About four times more light
leaves our farmlands than jungles. Nature is giving us a clue, by
example, of what is possible for the efficiency of light capture.
Imagine what we could do with our agriculture if we only captured
light with the same efficiency as the jungles? Might there be some
new way that yields similar use of photons? However, our agriculture
efficiency is very high as it is and includes another important
factor: time. Mature jungles take years to develop. We grow and
harvest our crops all within a few months. The kinds of plants we
raise for food crops require direct sunlight to do well. Delicate
orchids grown in deep shade do not yield much food value.
there is a trade-off between efficient use of light and the maximum
production of plant-derived biomass for food. It does seem that
our agriculture is well optimized for efficient production of food
but perhaps there is some room for some improvement, if we are only
willing to listen.