Saturday, October 15, 2016

Endangered plants, the population bomb, and politicians running for office

Cycads are gymnosperms that have survived from the dinosaur
era.  They are increasingly at risk of extinction from poaching
and habitat loss.  These Encephalartos brevifoliolata
from South Africa are already extinct in the wild.
Photo by Piet Vorster, CC BY-NC-SA 4.0 .
The cycad Encephalartos brevifoliolata is an endangered species.  In fact, it is already extinct in the wild, surviving only as a few specimens that had to be moved to a secure location.  Habitat loss and poaching for the horticultural trade threaten many species of cycads. These ancient gymnosperms are among the relatively few plants that exhibit complete gender distinction. Individual plants are either male or female, and as it happens, the surviving members of this species are all male.  Even if there were a female among them, their gene pool would be severely restricted, and future generations would be highly inbred.  With such limited genetic variation, recessive genetic defects are more likely to be expressed, and the entire population much more likely to succumb to disease or environmental change. Cacti, orchids, and carnivorous plants are other groups particularly threatened by poachers, but many other kinds of plants are equally threatened by loss of natural habitats to logging, agriculture, and "suburbanization."

More familiar examples of this are of animals.  Aside from the loss in numbers and other threats, concerns about the rare Florida panther center around its minimal genetic variation.  Animals in more vulnerable 
regions, such as rhinos, tigers, snow leopards, great apes, etc. face more immediate threats, but those that survive, possibly only in zoos, will face the genetic inbreeding problem as well.   Under such genetic constriction, the future of these species is in question.

Carnivorous plants around the world, like this Sarracenia rubra
in north Florida, face habitat loss and poaching by hobbyists.  
According to the Center for Biodiversity, a significant percentages of the Earth’s plants and animals are at risk of extinction, including 50% of the species of primates.  An estimated 1000 species of plants and animals that have already gone extinct under the watch of humanity (see The Extinction Crisis).  Again, animals are more familiar – dodos, passenger pigeons, etc., but 123 plant species have also been officially documented as going extinct in historical times (according to Wikipedia).  This is not to mention also the fact that possibly only half, or less, of the species of living organisms on this planet have even yet been documented by scientists, so we don’t know many that have already gone extinct or are endangered.  The present threat to the existence of organisms of all types, called the biodiversity crisis, could become a mass extinction greater than that in which the dinosaurs became extinct.

What are the consequences to the global ecosystem of plant and animal extinction?
This Dendrobium bracteosum was salvaged from the
branches of a tree felled for the timber industry in
Papua New Guinea in 1971.  Though widely cultivated,
what the fate of this species in the wild is today,
I do not know.
The loss of any species disrupts and simplifies the complex interactive web of life around us.  A plant that goes extinct may be the host or food source for dozens of other organisms, and likewise, an animal may be an important link in the food chain or a predator that keeps other animal populations in check.  Destabilized ecosystems are less productive, subject to wild fluctuations, suffer soil erosion, and become overrun by tough, weedy species of no use to anyone.  Loss of forests and the poisoning of photosynthetic algae in the oceans diminishes the replenishment of oxygen in our atmosphere, and the removal of carbon dioxide.

Why is all of this happening?  We might point to lack of regulation and enforcement, poor land management and forestry practices, human greed, and maybe the erroneous belief by many collectors that they are helping "save" rare species by growing them in their backyards.  But clearly, the growing human population, with its expanding demand for farmland, wood, clean water, and other natural resources, is directly related to the loss of natural habitats required by the others species we share this planet with. 

In 1968, Paul Ehrlich and his wife Anne (uncredited at the time) published The Population Bomb (Sierra Club/Ballantine Books, ISBN 1-56849-587-0), which warned of the dire consequences of uncontrolled and excessive growth of the human population.  They predicted widespread famine and other disasters as early as the 1970’s. The predictions were based on sound biological principles.  Every species tends to increase in numbers, because individuals have the potential to produce many more offspring than needed for their replacement.  In a balanced ecosystem, populations of each species are kept in check by limited food supply and other essential resources (e.g. nesting sites for some animals), by disease or predators, or by fouling their own environment.

The organ pipe cactus, Stenocereus thurberi,
is one of hundreds of cactus species that are 
Photo by Lars Hammar CC-BY-NC-SA 2.0
Though the Ehrlichs’ may have been off on the timing of some of their predictions (see their recent review article), the need to bring the human population under control is accepted by scientists and humanitarian groups in general.  The principle objections come from people who fear draconian governmental population control measures, or the impacts of no-growth economics.  Again, I can’t do a full review here, but a simple google search for either “overpopulation” or “underpopulation” will bring up a number of links (yes there are people who believe that we, at least in some countries, are underpopulated). 

Before I move on though, I must remark that while the world may not appear to be overpopulated from the biased perspective of affluent America, the 760 million people in the world who are currently undernourished, the 8,350,000 people who die of starvation each year (Worldometers), or the perennially impoverished people of Haiti who just suffered devastating losses from Hurricane Matthew, might beg to disagree.

Expanding numbers of desperately poor people encroach upon national parks and other wildlife preserves to find a means of livelihood, further endangering species and disrupting natural ecosystems.  Maybe we can support more people on this planet, but only by converting ever more wild land to food production.  As we attempt frantically to increase our food supply, we cut down more forests, irrigate deserts, and even encroach upon estuaries and marine habitats.  We also use more fertilizer, pesticides, hormones and antibiotics, keep animals in small cages, and continue to genetically modify our food crops. Watch the streaming statistics on Worldometers for a few minutes, you can also see that almost 4 million hectares of forest have been lost this year, and over 5 million hectares of soil have eroded away, along with other disturbing numbers that continue to increase.  And despite all the technological advances, if population continues to grow, we'll back to where we started, but with even more starving people, less wild land, and fewer species of plants and animals.

Adding the problems of air and water pollution, nuclear leaks, toxic waste dumps, and climate change, we are not only fouling our own nest, but that of wild plants and animals as well.  Coral reefs are dying around the world, as well as forests in the Appalachians and California mountains, honeybees are being poisoned, and tree frogs are dying from the effects of pollution.  As sea levels rise and ice caps disappear, not only are polar bears threatened, but also coastal estuarine communities (breeding grounds for many commercial fisheries), sea grass beds and lowland swamps, not to mention the billions of people who live in coastal cities. 

The human suffering is  front and center in our collective humanitarian consciousness, and protecting rare species may seem to be a luxury for the benefit of the affluent, but they are actually both manifestations of the same central problem.  Bringing population growth under control will benefit both people and biodiversity, and the sooner we do it, the better.

Instead of just trying to keep up with increasing population size with ever more technological fixes, maybe we should be asking how many people can the Earth sustain while providing a just and equitable distribution of resources to all of our inhabitants, and while maintaining a viable, biologically diverse ecosystem with which to sustain ourselves.  I would think that, just maybe, we already have enough people on this planet, maybe more than it can sustain cleanly with renewable resources over the long run. Perhaps even a small decline would be helpful in taking care of everyone already here and getting back into balance with our natural ecosystem.  After all, there are already 7.5 billion of us.  We have huge, possibly insurmountable problems to solve, which are only exacerbated if the population continues to grow.  So reducing global population growth should be on the table as a  topic of public discussion, right next to all the other problems that need to be solved. 

But it isn’t.  Outside of academic circles and activist blogs (both pro and con), the population problem is hardly ever mentioned.  It’s not in the mainstream media or in politics. And that brings me to the third part of my title.  As we face elections here in the U.S., or as some of you face them elsewhere, we must choose candidates who respect science, who are aware of the impact of population growth on world justice and on our planetary ecosystem, and who are willing to study and discuss these issues seriously.  They must also take the search for sustainable economics seriously.  Those who deny the existence of climate change and rising sea levels, who want to do away with environmental protection agencies, who oppose treaties on clean air and reduction of carbon emissions, and who want to open up national parks and other wild lands to mining and other economic exploitation, just don't get it, and must be rejected. 


  1. Thank you for the excellent post, Professor! Extinction, population growth and politicians who should know better, certainly the three go together.

    The book “Overdevelopment, Overpopulation, Overshoot,” to quote from the web site, “crystallizes the ecological and social tragedies of humanity’s ballooning numbers and consumption” in photos. It looks like it is still available for free to share with others. I gave my copy to my local library, but the photos are all online to view as well.


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