X-Message-Number: 0023
Subject: Saving The Library Of Life
Date: 06 Mar 93 13:43:50 EST
From: Charles Platt <>
Message-Subject: CRYONICS Rainforest Plan
To: Cryonet
March 6, 1993
Some people may be aware of the plan proposed last year by
Gregory Benford to freeze species which face extinction,
especially in tropical rainforests where slash-and-burn is in
progress.
With Benford's permission, I am posting the complete text of
his paper (about 24 kilobytes). There is reason to hope that
this very reasonable proposal by an accredited scientist will
encourage a slightly more receptive attitude toward cryonics.
--Charles Platt
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SAVING THE LIBRARY OF LIFE
Gregory Benford
Department of Physics
University of California, Irvine
Irvine, CA 92717
FAX: 714-856-5903
office: 714-856-5147
email:
Abstract
A broad program of freezing species in threatened ecospheres
could preserve biodiversity for eventual use by future
generations. Sampling without studying can lower costs
dramatically. Local labor can do most of the gathering.
Plausible costs of collecting and cryogenically suspending
the tropical rain forest species, at a sampling fraction of
10-6, are about two billion dollars for a full century. Much
more information than species DNA will be saved, allowing
future biotechnology to derive high information content and
perhaps even resurrect then-extinct species. A parallel
program of limited in situ preservation is essential to allow
later expression of frozen genomes in members of the same
genus. This is a broad proposal which should be debated
throughout the entire scientific community.
We have only begun the elementary taxonomic description
of the world biota. While about 1.4 million species have been
given scientific names, estimates of the total number of
species range up to roughly 30 million or higher (1,2).
Systematists may very well not know the species diversity of
the world flora and fauna to the nearest order of magnitude.
Time is running out in which we can even catalog our
living wealth. Though the overall extinction rate from fossil
evidence is of order 10-7 species per species year (3), a
very conservative estimate of the current extinction rate
gives roughly 5000 species lost annually (4), with some
values far higher (5,6).
We are accelerating toward a calamity unparalleled in
planetary history. The best known cause of present day
species extinction is the cutting of tropical forests, which
have lost about 55% of their original cover and are shrinking
at the rate of 1.8% per year (5). Worse, the rate seems
doomed to increase, since its ultimate cause is human
activity, and human numbers and expectations grow apace. To
improve the lot of a swelling human tropical population would
require at least a fivefold increase in economic activity
there, bringing a crushing load on the already strained
biosphere (6).
Other biological zones such a coral reefs and oceanic
islands also dwindle at alarming rates. Because of the
latitudinal species diversity gradient, losses are most
severe in precisely the tropical continents where our own
numbers swell so alarmingly (7).
Everywhere there are calls for a halt to tropical
deforestation, but most voices seem tinged with despair.
Ehrlich and Wilson suggest we could lose a quarter of all
species in half a century, with incalculable effects on our
biosphere (8). We now co-opt about 40% of plant growth
worldwide, favoring monocultural crops, which must greatly
affect genetic diversity. Given the blunt economic and
cultural forces at work, even slowing the rate of destruction
seems doubtful in the immediate future.
This dire moment demands radical thinking. In the spirit
of a thought experiment, I discuss here a proposal which
links the in situ preservation community, which emphasizes
protected wild areas, and the ex situ conservationists such
as zoos, botanical gardens, etc. For in situ measures there
are economic, environmental and aesthetic arguments. To
preserve the genome of many species, however, ex situ methods
may suffice. Considering this possibility serves to separate
the kinds of arguments we make for conservation methods,
including concepts of our moral debt to posterity. In the
spirit of sharpening debate by considering plausible
scenarios, we can test our ideas.
Salvage by Sampling
Our situation resembles a browser in the ancient library
at Alexandria, who suddenly notes that the trove he had begun
inspecting has caught fire. Already a wing has burned, and
the mobs outside seem certain to block any fire-fighting
crews. What to do? There is no time to patrol the aisles,
discerningly plucking forth a treatise of Aristotle, or
deciding whether to leave behind Alexander the Great's
laundry list. Instead, a better strategy is to run through
the remaining library, tossing texts into a basket at random,
sampling each section to give broad coverage. Perhaps it
would be wise to take smaller texts, in order to carry more,
and then flee into an unknown future.
While efforts to contain and control our accelerating
biodiversity disaster are admirable, and should be
strengthened, it may well be time to consider a similarly
desperate method of salvage. I propose that the biological
community ponder a systematic sampling of threatened natural
habitats, with long term storage by freezing. This would more
nearly resemble an emergency salvaging operation than an
inventory, for there would be minimal attention paid to
studying the sample. The total sample mass might be reduced
by judiciously trimming oft-repeated species of the prolific
ants and beetles. (Duplication in sampling makes for good
statistics, though, helps comparative anatomy, and may aid
those for whom more successful species are more interesting.)
The essential aim is to save what we can for future
generations, relying on their better biological technology to
extract the maximum benefit.
Sampling of tropical trees by insecticidal fogs and
active searching of the canopy is common. Teams trained to
simply collect, without analyzing, require minimal labor by
research biologists. Freezing at the site can be done with
ordinary ice or dry ice; liquid nitrogen suspension can occur
only at the long-term repository. Extensive work by
taxonomists enters only when samples are studied and
classified. Here lies our current bottleneck. There are far
too few taxonomists to tally the world's species within our
generation (6), let alone analyze them.
We sidestep this problem if our primary aim is to pass
on to later generations the essentials of our immense
biodiversity. Even information about the existence of a
species is useful, for without a sample, in the future one
cannot be sure whether a given variation did not exist at
all, or simply became extinct without being observed. Thus
extensive taxonomic expertise would defeat the project.
Detailing allelic variations within a population, or other
variations (con-specific, interpopulation; congeneric;
ecosystem, etc.) probably will not be worth the trouble.
It seems likely that captive breeding programs, parks,
microhabitats and zoos can preserve only a tiny fraction of
the threatened species. (Here I shall use the term
"preservation" to mean keeping alive representatives of at
least each genus--in situ, in vivo protection in reserves--
and argue that this is essential to eventually studying and
potentially resurrecting frozen species.)
To save the biosphere's genome heritage demands going
beyond existing piecemeal strategies of seed banks, of
germplasm and tissue culture collection, and cryopreservation
of gametes, zygotes and embryos; these programs mostly
concentrate on saving traditional domesticated varieties (8).
Our goal is a complete sample of all threatened species.
Cryoprotection
Much more than data about existence can be carried
forward by simply preserving a wide sample at low
temperatures. Banking cells by drying them with silica gels,
for example, is useful for short times, but at room
temperatures thermal damage to DNA will accumulate over the
decades. We know that seeds can germinate after lengthy
freezing, and that microbes can sustain cryogenic
temperatures. Simple cells such as sperm and ova survive
liquid nitrogen preservation and function after warming.
Generally, organs with large surface/volume ratios preserve
well, such as skin and intestines.
Of course, more complex systems suffer great freezing
damage, though research proceeds into minimizing this.
Several kinds of damage occur, and little is known about
methods of reversing such injury. Biochemical and biophysical
freezing injury arises from shrinking cell volume as freezing
proceeds. Plants display extrusion of pure lipid species from
the plasma membrane, as cells contract during freezing
(9,10). Such lipids do not spontaneously return to the plane
of the membrane during volume expansion on thawing, so that
restoration of approximate isotonic volume near the melting
point causes cellular lysis due to inadequate membrane
surface area. While osmotic injury can be reversed (11),
there is loss of membrane proteins (12). Reorganization of
membrane bilayer structure into cylindrical lipid tubes may
be reversible with warming (13, 14, 15). Structure of the
cytoplasm may break down into blobs of proteinaceous matter
(16, 17). Major fracturing of cells, axons, dendrites,
capillaries and other elements causes extensive damage at
temperatures below the glass point (18), suggesting that this
be avoided. For some purposes, then, immersion in liquid
nitrogen may be unacceptable.
The problem of recovering cells from frozen samples is
complex, but even low survival rates of one cell in a million
are irrelevant if the survivor cells can produce descendants.
However, our minimum aim can be to simply retain DNA, the
least we should expect from a sample--though of course,
suspending whole creatures retains far more information. For
this, liquid nitrogen is suitable for long term storage (-
196o C), especially since it is by far the cheapest method.
At 25 cents/liter, liquid nitrogen is the lowest-priced
commercial fluid, excepting water and crude oil. It allows
suspension in large, easily tended vaults, simply by topping
off the amount lost. Only a wholesale breakdown of industry
can plausibly destroy the samples; no mere power failure will
do. Redundant storage at different sites avoids even this.
Further, while neither liquid nitrogen nor freeze-drying
damage DNA, freeze-drying does cause far more injury to
structural and taxonomic characteristics. For the broad
program envisioned here, which should also include tiny
samples of ocean water with its teeming viruses and bacteria,
plainly liquid nitrogen is essential. This is also true for
saving whole creatures, since we also gain their parasites,
bacteria, and viruses, which are better preserved
cryogenically.
A crucial point is that we need not rely on present
technology for the retrieval. Progress in biological recovery
can open unsuspected pathways.
Recent advances underline this expectation. Techniques
such as the polymerase chain reaction can amplify rare
segments of DNA over a million-fold (19). Such methods have
enabled resourceful biologists to recover specific segments
from such seemingly unlikely sources as a 120-year-old museum
specimen, which yielded mitochondrial DNA of a quagga, an
extinct beast that looks like a cross between a horse and a
zebra (20). A 5000-year-old Egyptian mummy has yielded up its
genetic secrets (21). Amplifiable DNA in old bone is
beginning to open study of the bulk of surviving organic
matter from the deep past (22). The current record for
bringing the past alive in the genetic sense is DNA extracted
from a fossilized magnolia leaf between 17 and 20 million
years old (23). This feat defied the prediction from in vitro
estimates of spontaneous hydrolysis rates, which held that
DNA could not survive intact beyond about 10,000 years (24).
We should recognize that future biological technology
will probably greatly surpass ours, perhaps exceeding even
what we can plausibly imagine. Our attitude should resemble
that of archeology, in which a fraction of a site is
deliberately not excavated, assuming that future
archaeologists will be able to learn more from it than we
can.
Preserve the Genus, Freeze the Species
We need a combined strategy to salvage biodiversity out
of catastrophe. The best approach may be two-pronged:
(a) preserving alive some fraction of each ecosystem
type ("biome"), its population intact at the genus level, and
(b) freezing as many species related to the preserved
system as possible.
At a minimum, this will allow future biologists to
extract DNA from frozen samples and study the exact genetic
source of biodiversity. Genes of interest could be expressed
in living examples of the same genus, by systematic
replacement of elements of the genetic code with information
from the frozen DNA. Obviously, the preserved genus is
essential.
These techniques would open broad attacks on the problem
of inbred species. A ravaged environment can constrict the
genetic diversity of individual species. Reintroducing
diverse traits from frozen tissue samples could help such a
species blossom anew, increasing its resistance to disease
and the random shocks of life.
Beyond this minimum--the DNA itself--future biologists
will probably find great use for recovered cells in re-
expressing a frozen genome. Cell use for mollusks, trees,
insects etc. is a cloudy, complicated issue. For mammals,
uterine walls, elements of the sexual reproductive apparatus,
etc., should prove essential, since placentation and the
highly variable physiology of different taxa are crucial. It
seems highly unlikely that one can make appropriate placental
and endometrial choices in the many steps from genome to
newborn, merely from reading DNA.
As saviors of the "Library of Life" we are at best
marginally literate, hoping that our children will be better
readers, and wiser ones. Many biotechnological feats will
probably emerge within a few decades--many ways, let us say,
of reading and using the same genetic "texts." But no
advanced "reader" and "editor" can work upon texts we have
lost.
This holds out the hope of selectively reintroducing
biodiversity in the future, to gradually recover lost
ecosystems. Individual species can be resurrected from very
small numbers of survivors, as the nearly extinct California
condor and black-footed ferret have been.
Fidelity in reproducing a genome may not be perfect, of
course. Many practical problems arise (placenta environment,
chemistry, etc.) which complicate expression of a genotype.
In any case, future generations may well wish to edit and
shape genetically those species within an ecosystem as they
repair it, for purposes we cannot anticipate.
Loss of nearly all of an ecosystem would require a huge
regrowth program, for which the Library of Life would prove
essential. Suppose, though, that we manage to save a large
fraction of a system. Then the species library will provide a
genetic "snapshot" of biodiversity at a given time and place,
which evolutionary biologists can compare with the system as
it has evolved much later -- for example, through perhaps
thousands of insect generations. This would be a new form of
research tool.
Already a crash program to collect permanent cell lines,
DNA, or both from vanishing human populations has excited
attention (25). This program maintains cell lines by
continuous culture, a costly method which invites random
mutation. Such records may allow a deeper understanding of
our own origins and predispositions (26), but banking frozen
tissues of endangered species is the only way to ensure that
any genetic disease diagnosed in the future in small, closed
populations (the "founder effect") can be mapped and managed
(27). Ehrlich suggested creation of "artificial fossils" in
such fashion (28). The "frozen zoo" of San Diego, begun with
this in mind (29), has immersed 2400 mammal fibroblast cell
cultures and 145 tissue pieces in liquid nitrogen--about 300
species, in all. Cryonic mouse embryo banking for genetic
studies is now routine (30).
The far larger prospect of eventually reading and using
a Library of Life is difficult for us to imagine or
anticipate, at the early stages of a revolution in biological
technology. Our situation may resemble the Wright brothers if
they had tried to envision a moon landing within three
generations. Can We Afford It?
This sweeping proposal avoids the problem of deciding
which species are of probable use to us, or are crucial to
biodiversity. By sampling everything we can, we avoid some
pitfalls of our present ignorance. Too often, preservation
efforts focus on "charismatic vertebrates," neglecting the
great bulk of diversity (8).
Many conservationists may be reluctant to support a
cryopreservation campaign, because they fear it will sample
too sparsely. This assumes that present taxonomic methods and
costs are necessary. But an important feature of this
proposal is that the samples need not be studied as they are
taken. This avoids the scarcity of taxonomists, speeding
field work and lowering costs. Plausibly, much of the
gathering can be done with semi-skilled labor.
This suggests immediately that the bulk of the funding
come from "debt swap" between tropical and temperate nations,
as has been used to "buy" rain forests and set them aside
from cutting (8). Further, this will create a local work
force which profits from controlled, legal forest work,
rather than from cutting it.
As a very rough estimate, consider a sampling program
which collects all life forms from a stand of a hundred
trees, but not the trees themselves, for each hundred square
kilometers of rain forest, i.e., a sampling fraction in the
range of 10-6. If this costs on average ten thousand dollars
per stand (probably an overestimate), then a million square
kilometers yields 104 stand-samples costing 108 dollars. For
all the world's tropical forests, covering about nine million
kilometers, the cost is close to a billion dollars.
To suspend such samples requires replacing boiled-off
liquid nitrogen. Suppose we collect ten kg. from each tree,
or about 107 kg. for a million-kilometer area. Current
nitrogen loss costs of a mass M presently obey a scaling law,
cost/year = $400/year (M/100 kg.)2/3
since nitrogen loss scales with surface area. To suspend the
stand-samples for all the tropical forests then demands 3.7 x
106 dollars/year, or 0.37 billion dollars for a century. A
similar argument suggests that building the repository,
curatorial labor, etc. will probably require comparable
costs, especially if the samples are to be readily available
to researchers, with detailed labeling. Thus an estimate of
perhaps a billion dollars for a century's storage seems
plausible. Added to the collecting cost, we need in sum about
two billion dollars. Current outstanding debt by tropical
nations well exceeds a hundred billion dollars.
Of course, this does not touch upon side costs in
training biologists, transport, perhaps doing some taxon
discrimination, etc. Certainly the effort compares in cost
with the Human Genome Project. The task is monumental; so is
the plausible benefit.
Traditional economics cannot deal with transactions
carried out between generations. As Harold Morowitz has
remarked, the deep answer to "How much is a species worth?"
is "What kind of world do you want to live in?" (31).
Counter-Arguments
This drastic proposal does not address many legitimate
reasons for preserving ecospheres intact, and it should not
be seen as opposing them. Indeed, only by preserving in vivo
a wide cross section of biota can we plausibly use much of
the genetic library frozen in vitro.
An obvious possibility is that preservation of habitat
may compete politically with a sampling and freezing program.
There is no intrinsic reason why this need be so. They are
not logically part of a zero-sum game because they yield
different benefits over different time scales. Of course we
would all prefer a world which preserves everything. But the
emotional appeal of preservation should not disguise the
simple fact that we are losing the battle, or to argue
against a prudent suspension strategy.
Further, sampling is far less expensive than
preservation--which is why it is more likely to succeed over
the long run. Even competition for 'debt swap' funds will not
necessarily be of the same economic kind. Conservationists
seek to buy land and set up reserves, putting funds into the
hands of (often wealthy) landowners. A freezing program will
more strongly spur local, largely unskilled employment,
affecting a different economic faction.
Sampling and freezing have little aesthetic appeal. To
some they will smack of fatalism; it may be merely realism.
As well, freezing species does not offer the immediate
benefits which preservation yields. (Samples would probably
be taken only from areas not already highly damaged.) More
concretely, this proposal will not hasten benefits from new
foods, medicines, or industrial goods. It will not alter the
essential services an ecosphere provides to maintenance of
the biosphere. We should make very clear that this task is
explicitly designed to benefit humanity as a whole, once this
age of rampant species extinction is over.
Some will see in this idea a slippery slope: to
undertake salvaging operations weakens arguments for
biodiversity preservation. To avoid this, the two parallel
programs of preservation and freezing must be kept clear. In
this sense the analogy to the library at Alexandria is false-
-for us, there is no true conflict between fighting the fire
and salvaging texts. Further, in the real world, funds for
conservation of DNA today do not come directly from in situ
programs. If the Topeka Zoo budget is cut, the city does not
transfer funds to Zaire to save gorillas.
Indeed, one can make the opposite argument -- that the
spectacle of the scientific community starting a sampling
program will powerfully illuminate the calamity we face,
alerting the world, stimulating other actions. Beginning with
local volunteer labor and contributions -- say, with the
Sierra club sampling the redwood habitat -- could generate
grass-roots momentum to overcome the familiar government
inertia. In larger campaigns, by requiring that samplers
accompany all legal logging operations, we can help develop a
local constituency for controlled harvesting.
Perhaps the most difficult argument to counter is
basically an unspoken attitude. As scientists we are trained
to be careful, scrupulous of overstating our results, wary of
speculation--yet these militate against the talents needed to
contemplate and prepare for a future which can be
qualitatively different from our concrete present.
Paradoxically, we scientists labor to bring about this
changed future. Now is the time to bank on the expectation
that we will probably succeed.
Leading figures in biodiversity argue that a large scale
species dieback seems inevitable, leading to a blighted world
which will eventually learn the price of such folly (6, 8,
30). The political impact of such a disaster will be immense.
Politics comes and goes, but extinction is forever. We may be
judged harshly by our grandchildren, our era labeled the
Great Dying or the Age of Appetite.
A future generation could well reach out for means to
recover their lost biological heritage. If scientific
progress has followed the paths many envision today, they
will have the means to perform seeming miracles. They will
have developed ethical and social mechanisms we cannot guess,
but we can prepare now the broad outlines of a recovery
strategy, simply by banking biological information.
Such measures should be debated, not merely by
biologists, but by the entire scientific community and
beyond, for all our children will be affected. These are the
crucial years for us to act, as the Library of Life burns
furiously around us, throughout the world.
Acknowledgements
I am indebted to those who contributed valuable comments and
ideas to this proposal: Mark Martin, Oliver Morton, Steve Harris,
David Brin, Oliver Ryder, Kurt Benirschke, Harold Morowitz,
Murray Gell-Mann, Gregory Fahy, Hugh Hixon, Michael Soule',
Francisco Ayala and Bruce Murray.
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