As organisms became more complex, evolving
into plants and animals, they began to colonize shorelines creating microbial
mats that soon spread inland diversifying into a great variety of fungi,
lichens, and mosses. The early moss
created wetland bogs, creating a buildup of dead organic material known as
peat. We can speculate that on occasion
in times of drought, these bogs dried out on the early earth and burned,
ignited by lighting just as they do today.
In such a manner the bog, rejuvenated by fire, fills up with open water
when the rains come, and the process of succession begins anew.
Over hundreds of millions of years the
continental tectonic plates have drifted all over the globe. This drift has created vast super continents
like Pangaea where species mingled together. Some species perished, and others
flourished as they competed and cooperated among themselves for life's
necessities. When the continents drifted
apart, this sent different species on different evolutionary trajectories
caused by changing environmental and genetic conditions in different locations
and climate conditions.
Over thousands, millions, and hundreds of
millions of years the climate was fluctuated extensively from very warm to very
cold. The cause could be external impacts like asteroid impacts, massive
volcanic eruptions, continental drift, and even massive global change caused by
the evolution of life itself. For
instance some scientists speculate that one global ice age was caused by the
colonization of the land by mosses. This
in turn caused atmospheric changes plunging the whole earth into a deep freeze,
causing the extinction of 90% of the animals and plants at the time.
Through it all there was always fire, just
as much a force of nature affecting natural ecosystems as is climate, water,
atmosphere, and continental drift. It is
obvious that when vegetation dies it either must decompose or burn. In warm, moist environments as in the tropics
it can quickly decompose. In drier climates decomposition is much slower. Fire
allows nutrients to quickly get back into the soil, reduces plant and animal
diseases and pests, and eliminates the mulching out of new growth.
Sometimes the vegetative fires during
geologic times were diminished, as during ice ages and when oxygen levels were
low, and sometimes fires were very prominent and frequent, when oxygen levels
were high and the earth warm as in the carboniferous and cretaceous. During these periods of warm climate just
about every kind of plant and animal developed adaptations to fire, becoming
fire dependent.
Most people today are unaware of the
critical importance of fire in nature's ecosystems and this has led to severe
environmental consequences for all life on earth including man. It is imperative that environmentalists,
politicians, and land managers both public and private understand this
critical role of fire in the environment in order to adequately preserve and
protect the fragmented ecosystems still remaining on earth.
Most ecosystems around the globe are so
fragmented by modern man that light natural fires can no longer be allowed to
burn freely and frequently as they have for hundreds of millions of years. This
has resulted in huge unnatural catastrophic accumulations of fuel in forests,
savannas, and grasslands. Sooner or later
these fuel loads will be ignited by lightning, or by man, forcing huge
unstoppable catastrophic fires damaging to both nature and man.
So the remedy for fire in the environment is not more fire suppression, but controlled or prescribed fire to simulate natural fire. Plant and animal life adapted and used fire for competitive advantage for at least 420 million years as evidenced in the fossil record. This has created a wide spectrum of planetary diversity from very many plants with at least some fire resistance, to a very few, very fire-tender plant species and their animals dependent on these ecosystems.
During the fiery carboniferous period of
geologic history oxygen levels were much higher than they are today. These higher oxygen levels allowed dead
vegetation accumulating in early forests and savannas to burn much better than
even today. Many species of plants like
the palms evolved very fire-resistant trunks to protect against frequent ground
fires. But these early forest plants
went even further to use fire to their competitive advantage.
The palms evolved flammable fronds that
when the individual fronds died and fell to the ground they burned out the
competition. By becoming so fire adapted
they thrived at the expense of their competitors and so became a fire-dominant
species, spreading all across the supercontinent of Pangaea. Other palm species like the palmetto and the ferns
closer to the ground formed the understory and adapted by developing flammable
fronds and strong underground root systems. When frequent fires burned, killing everything close
above ground, they quickly sprouted back using the energy reserves stored in
their roots.
Later, pine trees evolving in the fiery
cretaceous when oxygen levels were again very high evolved thick insulating
bark and flammable needles, following the example of the palms using fire to
burn out the competition. Later the
grasses evolved in these high-fire environments and used the same fire-adapted
natural strategies as had the ferns, palms, pines, and palmetto, to burn out
the competitions and to sprout back quickly after a fire and grazing.
In a short span of only a few days after a
rain, a blackened burn will once again become green. The grasses sprout from their fire-protected
roots underground, in the same manner following the example of the palmetto and
the ferns. Additionally, the fresh ash
with the first rain soaks into the soil giving this new growth even more
vitality.
All this time while the plants were
evolving in fire ecosystems in Pangaea and Gondwanaland the land animals were
not standing still. They were also
adapting to low-intensity and occasional catastrophic fires. The best I can tell the ocean arthropods
began moving onto land as they do today to colonize and feed on the detritus
being washed up on beaches and in lagoons where early ocean plants were also
taking root. These early arthropods
evolved into the insects we have today and went from jumping, to gliding, to
flying, to get around and to feed on fresh vegetation and other insects on
land. In the carboniferous the fishes
followed the insects onto land and evolving into amphibians and reptiles.
I would speculate that one of the reasons
that insects developed wings was to get out of the way of frequent ground fires
as well as predators. They also could
dig into the damp ground or crawl down in openings at the base of plants. The amphibians and reptiles had to use other
strategies like fast flight, or diving into water to avoid getting burned. It was not until the dinosaurs developed
wings that land animals were able to fly to avoid fire, or to fly back into the
blackened burn to forage for roasted insects and small reptiles and small mammals
now openly exposed to view.
Most people all over the world know about
the almost indestructible palmetto bug or cockroach. Well, it's an example of a very well-adapted
fire species that evolved in the carboniferous among the palm trees and the
palmetto. Cockroaches are able to scurry
down into the ground, or fly away to avoid fire, only to quickly return to feed
on the greening vegetation and any other insects that might have not been so
well adapted.
I cannot but be impressed, when we
simulate natural low-intensity fires in fragmented ecosystems, that we are
burning through a mosaic of ancient and modern plant and animal species. In a layering process over hundreds of
millions of years, newly evolving species of plants and animals enter the
ecosystem, forcing out less adaptable species.
However, when new species evolve in the ecosystem, they often do not
always destroy earlier plants and animals that continue to successfully
adapt. The older species may simply be
pressured into moving into new niches being created by the newer invading
species.
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