Searching for Nature
Defining a reference condition?
Should we stop time?
Demiurges
Prostheses and bionics
To conclude
The "nature of Nature" is still uncertain and is at the base of many
debates.
Changes aimed at enhancing the value of natural habitats, even when ecologically
sound or when seeking to recreate more "natural" habitats, are often viewed
as "unnatural". A consequence is that any reflection about the nature of
Nature is thus underpinned by the dichotomy between Man and Nature.
To avoid being unduly categorical, I shall discuss several well-documented
examples and use them to draw some conclusions.
An article by Pearce (2000) raises interesting questions about the case of
Africa. Do the great natural parks of Africa correspond to a natural environment
or a totally artificial landscape? From this point of view, the ecological
catastrophe that hit a large part of the continent at the end of the XIXth
century is edifying.
In 1887, an Italian military expedition brought cattle plague to Eritrea,
formerly spared by the disease. This Central Asian virus very quickly spread
over all East and Southern Africa and, in just a few years, the death rate
of cattle was estimated at 90%. And the percentage was most probably higher
in certain regions. For instance, of the 400 000 cattle present in the region
of Lake Victoria in 1891, only 20 000 were left the year after. Wild animals
were also hit by cattle plague as they had no natural immunity to the virus,
especially ungulates that only became totally resistant around 1960. Many
studies are available in the literature on the restoration of animal wildlife
and the evolution of carnivores.
Awareness of this major catastrophe is cardinal for our discussion. It's
importance for African wildlife and for the pastoral cultures and their
environment is not to be underestimated.
On the human scale, it caused considerable disruptions: famines, epidemics,
wars, social destabilisation, etc.
In the years that followed, the absence of pastoralism had several
consequences:
- traditional grazing land vegetation was replaced by bushes and other woody
plants.
- animal wildlife was quickly restored, despite the relative sensitivity
of ungulates to the disease.
- the tsetse fly rapidly increased in number due to a favourable environment
brought on by these changes.
- and as a consequence, sleeping sickness, dangerous for both humans and
cattle, rapidly spread.
The impact of this disease is often underestimated: it caused several million
dead at the beginning of the century and still takes 100 000 human lives
each year. The disease therefore makes the settlement of herders in the most
infected areas extremely difficult. For the most cynical, tsetse flies are
considered the best gamekeepers in Africa.
This Africa, ruined and depopulated by the disease, made a great impression
on the first conservationists who visited the continent. However, a little
later, Julian Huxley wrote about a "rich natural world, as it was before
the advent of modern Man". Even for those who were aware of the negative
impact of the epizootic disease, the idea of inescapably returning to an
original climactic vegetation came across as an infallible scientific truth.
And this is how the great African parks were created and why people and their
cattle were to remain permanently excluded from these areas.
For example, Grzimek, one of the most active conservationists, was intent
on driving the Masai tribe out of the Serengeti national park: no human being,
not even a native, should live inside its boundaries.
It has since been proved that, in this case, the notion of climax is rather
simplistic and cannot easily explain the evolution of African savannahs.
Their natural evolution seems to be extremely dynamic, entailing considerable
changes in a short time span, ten or twenty years for example.
In the framework of nature management, we are thus offered the following
choice. We can opt for the present aspect of the great African national parks,
with their thriving woody vegetation, abundant wildlife and overly abundant
tsetse flies; or we can opt for a landscape that has existed for several
centuries and that still occurs here and there, where people and their cattle
prevail and where both the bush and tsetse flies are under control. To tell
the truth, there is a third solution that Pearce does not refer to. It consists
in returning to the ecosystems that existed before humans became an important
factor in their evolution.
Without dealing with the social factor (in spite of its importance), I would
now like to raise the question of "naturalness" and "artificialness" in the
territories that we are trying to protect.
[R].Defining a reference condition?
I do not wish to elaborate here on the difference between good and evil,
contrary to certain "nature philosophers". My only ambition is to explain
some scientific certainties concerning a certain natural state considered
as a reference condition. We owe these certainties to the implementation
of a number of techniques, such as the study of pollen deposits in the soil
or that of charcoal or gastropod shells. The date chosen to define the reference
state is one of the main questions raised.
A certain logic would consist in choosing the beginning of the present climatic
phase, the sub-Atlantic phase, set at 700 years B.C. and characterised by
the important development of hornbeam and oak in France. However, the major
changes linked to human activities, especially in the South, occurred well
before this date. Therefore, the reference state is not always easy to determine.
Setting the date after the last main natural climatic changes, means setting
the date after the first changes caused by Man!
One can find literature describing the influence of Man on the landscape
far before the onset of the sub-Atlantic phase (see, for example,
Renault-Miskovsky, 1991).
Setting a date for the reference condition is often a rough and ready settlement,
but as long as one is aware of this, the notion remains useful.
Sometimes, the chosen reference state is not all that old. Take, for example,
the attempts to restore the function of the alluvial habitats of the Rhine
river; the reference state chosen was that of the river before the rectification
works of the XIXth century.
Moreover, one must remember that our topic, Nature, is not static but
dynamic.
On the other hand, a species that existed several million years ago can still
exist, but may have undergone several changes. Moore (1987) observed that
the separation of Great Britain from the Continent, roughly 7000 years ago,
induced many differentiations. The French grey wagtail exists on the other
side of the Channel but is much darker than on the continent and the yellow
wagtail has lost the blue colouring on its head.
These external changes are probably accompanied by physiological and behavioural
changes, less obvious to the eye. If we compared the genetic diversity of
the same Linnaean species over a period of time we would definitely be surprised.
Given the above facts, this is a good question to ask.
When concluding on an important research operation on the restoration of
limestone ecosystems, in Normandy and Lorraine, Alard (2001) revealed the
existence of a more or less ancient forested period on all the sites studied.
In their present state, these environments are the fruit of agricultural
activities. Moreover, in most cases, a phase of pastoralism was most often
preceded by a cultivation phase. The author clearly shows that the decision
to conserve or restore these environments does not rest on "natural" aspects.
On the other hand, composition, originality and organisation have been taken
into account. Without going into detail, we can nevertheless say that, although
there are not more species than elsewhere, chalk grasslands especially contribute
to landscape diversity and thus to regional biodiversity. The decision to
conserve these chalk grasslands can therefore be entirely justified, although
going counter natural processes such as colonisation by woody species and
competition with grass species.
This is not an isolated case. The dry grasslands of the Causse Méjan
(a limestone plateau in the South of France), being restored under the
responsibility of the Cévennes national park, are often considered
to result from ancient agro-pastoral activities.
Other questions nevertheless remain unanswered. Where do the animal and plant
species living on these grasslands come from? Where can we find similar natural
environments? As regards the hills overlooking the Seine River, M. Bournerias
(in litt.) suggests that some of the grasslands clinging to the steep
slopes of these cliffs are extremely old. There would be a lot to learn by
studying the "primary habitats" at the base of the colonisation of man-made
environments.
The wish to conserve a rich biodiversity, closely linked to human activities,
is certainly wide-spread. But it often goes hand in hand with the wish to
block the evolution of an environment so as to conserve a certain stage of
evolution considered worthy of interest, for as long as possible. In 2001,
the Brière regional park, a marshland area north of the Loire river
estuary, decided to fight the silting process due to decomposition of the
marsh vegetation by exploiting it. It was argued that the silting up of the
area would entail ecological consequences, amongst others. The development
of woody vegetation, the argument ran, would lead to a great loss of
biodiversity. Since this is not a scientific article, I will not compare
the biodiversities of marshlands and wooded marshes. I simply wish to use
this example, in an objective manner, to show that the conservation of a
present state, and even the search for a former one, is an extremely strong
motivation.
However, a degree of respect of the diversity of vegetation successions is
required, even though certain stages may be less "pleasant" than others:
disruptions caused to the dynamics of habitats need to be considered and
discussed.
It must be added that human modification of habitats does not always have
a negative effect on biodiversity.
Thomas (1993) estimated that when temperatures decreased about 6000 years
ago, 18% of the 55 Rhopalocera species (Lepidoptera) in Great Britain only
survived thanks to the warmer microclimates created by agriculture and
pastoralism. The ecological interest of hedgerows, for example, is obvious.
These considerations led me to propose the expression "ordinary nature" at
a seminar to refer to the biocenoses that contain no or few rare or endangered
species but which have their own values, for example, owing to their area
extent.
The evolution of agricultural land use and of farming practices are thus
important and must be taken into consideration.
We can also add that the condition of "ordinariness" may also evolve. The
"ordinary" can quickly become important. Take the example of crop "weeds"
such as cornflowers.!
From time to time, an unremarkable environment may become the home of a species
with a so-called strong patrimonial value: it has settled there for lack
of a more natural habitat. Little Bustards, for example, nest in arable crop
areas of the Maine-et-Loire department in western France and "wild" tulips
grow in the Lubéron vineyards (France).
Such areas are however often not considered to be "natural nature" and, for
a long time, ecologists ignored these so-called "denatured" areas, which
has had rather negative consequences (Drury, 1998).
Fortunately for biodiversity, many species do not require a rich and balanced
ecosystem and are satisfied with those providing the essential elements of
their ecological needs. Many migratory birds spend the winter on manmade
lakes. The purification lagoons in Rochefort (France) attract an impressive
number of Anatidae.
In certain cases, this can encourage nesting. For instance dug sites for
aggregates in the main bed of the Loire river to build a motorway, rapidly
and with no particular redesigning became the home of Mediterranean Gulls,
with roughly 160 nesting couples recorded in 2001.
Of course, in both cases, food can be found at a reasonable distance and
this is obviously an essential condition.
Sometimes, when nature is lacking, we do not hesitate to create it. "Ecological
engineering" not only helps repair and restore, but also builds anew. A good
example is that of the rehabilitation of quarries (Frochot, 2001). Whether
they are meant to remain dry sites or turned into aquatic environments, they
will necessarily evolve over time. The ecological successions that will take
place must be foreseen and controlled, especially in order to optimise their
ecological value. Moreover, the knowledge acquired during these diverse
operations is enough justification in itself.
We must however be aware that our possibilities are limited, especially by
the size of the areas where we can intervene. A good illustration is that
of Père David's Deer (Elaphurus davidianus): this animal was
long confined to an imperial park in China and is present in many zoos, but
will never return to its natural habitat which has been transformed by
agriculture. Not everything is reversible, in spite of the valuable work
of these demiurges, even though many species can adapt to these recreated
environments.
The wish to conserve nature is often impeded by the lack of certain essential
features normally ensuring the functionality of the whole system. Creating
artificial structures can sometimes improve the state of things: such structures
are generally known as "prosthesis".
Such are for example the "fishways" that help migrating fish swim up barrage
works, the corridors which link protected areas together or the "wildlife
passages" that enable game animals to cross linear obstacles such as motorways.
The structures designed to reconnect the alluvial areas of the Rhine with
the channelled river bed so as to recreate periodic flooding of these areas
come under in this category.
Sometimes we go even further. The rehabilitation of the Seine estuary is
a good example. This estuary is subject to a lot of contrasted attention.
On the one hand, it is an expanding port (Le Havre, Rouen) and is of undeniable
economic importance. On the other hand, it is an area of great productivity,
especially for fishing. Moreover, the estuary plays a major international
role especially as regards bird biodiversity. A rather fragile structure
has been set up to try and conciliate these different functions. This structure
consists in maintaining the channels, building wharfs and other port facilities.
It also consists in creating artificial islands, rest places for birds, and
mudflats, which provide food for the aquatic organisms and birds linked to
the tidal patterns. Last but not least, it consists in a natural reserve
of 8500 hectares, embedded in an artificial universe.
We are thus moving closer to bionic structures, part-biological, part-machine,
which are subject to much research, even if the idea does not yet satisfy
traditionalist naturalists.
Natural nature, static nature, organised nature, manmade nature,
artificial nature. There are many types of nature that are not always easily
identified.
I recently tried to show the importance of the three attributes of an ecosystem:
biodiversity, naturality and functionality (Lecomte, 2001). Naturality is
generally the most sacrificed of these attributes (Lecomte, 1999). An in-depth
study has shown that naturality is rare in metropolitan France.
Thus, each person may decide what he or she considers to be Nature. A certain
intellectual honesty is nevertheless required, especially as concerns the
past history of habitats.
Although I am deeply convinced of the importance of the grasslands that have
replaced forest environments following human activities, I refuse to consider
them as the last remnants of an ancestral steppe!
[R]. Bibliographical references
Alard D., 2001. Déterminisme et restauration de la biodiversité
des écosystèmes calcicoles dans la moitié Nord de la
France ( Normandie et Lorraine). In J.-L. Chapuis, V. Barre, G. Barnaud :
Recréer la nature. MATE, p. 95-102.
Drury W.H., 1998. Chance and change. Ecology for conservationists.
Univ. of California Press, 223 p.
Frochot B., 2001. Intérêt écologique et implication
économique des réaménagements de carrières,
méthodes d'évaluation et d'étude des trajectoires et
vitesses d'évolution. In J.-L. Chapuis, V. Barre, G. Barnaud
: Recréer la nature. MATE, 128-134.
Lecomte J., 1999. Réflexions sur la naturalité. Courrier
de l'environnement de l'INRA, 37, 6-10.
Lecomte J., 2001. Conservation de la nature : des concepts à l'action.
Courrier de l'environnement de l'INRA, 43, 59-73.
Moore N.W., 1987. The bird of time. Cambridge univ. Press, 290 p.
Parc naturel régional de Brière, 2001. Sortir du noir.
Parcs, 42, 17-18.
Pearce F., 2000. Inventing Africa. New scientist, 12.08, 30-33.
Renault-Miskovky J., 1991. L'environnement au temps de la
préhistoire. Masson, Paris, 200 p.
Thomas J.A. 1993. Holocene climate changes and warm man-made refugia may
explain why a sixth of British butterflies possess unnatural early-successional
habitats. Ecography, 16(3), 278-84
[R].
