What Are the Major Threats to Biodiversity?

Life on earth is nothing, if not resilient.Trillions of species have arisen and vanished into extinction on planet earth and even following each of five mass extinctions, life has reborn and evolved to where we are today. 

So why worry about the recent rapid loss of biodiversity?

Because it may mean the end of our species, homo sapiens.  We have shown a good deal of recklessness in maintaining our position at the top of the food chain. 

Why does biodiversity matter?

Biodiversity is the variety of life on Earth at all its levels, from genes to ecosystems.  

Let’s consider a simplified example of the biodiversity within a tropical rainforest ecosystem.  Imagine that this wet, colorful ecosystem contains monkeys, birds, snakes, tigers, frogs, butterflies and other insects, tall trees, epiphytes with huge flowers and millions of microorganisms, bacteria and fungi. 

Some of the frogs may have a poisonous coating that kills some predators, but other predators may have evolved so that the toxin does not affect them. Likewise, some flowers may kill certain species of insects upon contact but not harm its pollinators. 

The adaptations life has evolved within the ecosystem keep the populations in balance so that the ecosystem can support them. 

We are all familiar to some degree with the web of life supporting us. We rely on plants, marine life and land animals for food. We rely on plants for our medicines.

But do we even realize how much we rely on intact ecosystems to purify and replenish the air we need to breathe, the water we need to drink and the land upon which we grow our food?

For the past two hundred years, we have been destroying these ecosystems and exterminating plants and animals at an unprecedented rate. Unfortunately, we cannot undo this. 

We cannot buy an ecosystem. Even with all of our amazing technological advances since the industrial revolution, we cannot simulate the natural world at any meaningful scale to preserve our species.  We cannot manufacture the clean air, clean water or fertile soil we need to survive.  We cannot recreate the biological processes allowing genetic adaptation. 

If we destroy the life that sustains our biosphere before we are able to adapt to the new world order that we are creating, homo sapiens will not survive.

The present rate of extinction of all species is catastrophic, one thousand times higher than it would be if not for humans [1]. 

This loss of biodiversity is considered the single greatest problem in conservation ecology [2].

What is the greatest threat to biodiversity?

Taking a step back then, we can see that the biggest threat to biodiversity is the exponential population growth of homo sapiens and consequent urbanization. 

In meeting our demands for food, shelter, clothing and consumer goods, we are destroying the of habitats of other species without check. 

We are:

• wholesale clearing forests and wetlands
• overfishing
• overhunting
• polluting the air, water and soil to toxic levels

Many scientists believe that we are already in the midst of The Sixth Mass Extinction, that homo sapiens are not going to be able to adapt in time to the compromised air, water and soil quality, to food laced with toxins and the tempestuous weather changes catalyzed by the excess heat of burning so much fossil fuel. 

Our demise will be caused by our thoughtless destruction of the very biodiversity that supports life. And so the logical first step to assure survival of our species is a preventive measure:  Halt the population growth.

We have 7.6 billion people, with 83 more million born tomorrow and 83 more million each successive day, needing food, clothing, shelter and wanting more and more consumer goods.  Our biosphere, the air within which we can live is a thin band, only around 20 kilometers high.

The loss of biodiversity from the way we are filling the needs and desires of over seven and a half billion people is at a tipping point.

And yet, the most recent estimate is that there will be ten billion of us vying for resources by 2050.  Not only is the population growing, but along with it desire for more and more consumer goods and fast, cheap food. 

In 1960, the average family owned one car.  The average two-bedroom apartment had two small closets.  The average home had one television.  Stores were not open seven days a week or 24/7.  Fast food chains were not as ubiquitous.

Sixty years later, there is no looking back. 

Manufacturing and transporting all of the items consumers demand is achieved through burning a tremendous amount of fossil fuel.  While some air pollution controls are in place for industrial discharge of emissions from manufacturing and generating power in developed countries, transportation industry, regulations are largely unenforced although they contribute 45 percent of the putrid air pollution enshrouding American cities.  

Huge tractor trailer and construction trucks spew thick black smelly smoke unapologetically.  Air quality in modern countries remains subpar and in developing countries it is critically poor, with soaring rates of chronic obstructive pulmonary distress and cardiovascular diseases and routine spikes in hospital admissions during the increasingly frequent acute air pollution episodes [3].

Water quality is suffering from the atmospheric deposition of the noxious chemicals spewed into the air and discharges onto the land and into waters.  

The land is not faring any better from clearing for housing developments, manufacturing industries, agribusiness and urban sprawl and the dumping of poisonous chemicals, waste products of all of these activities.

The correlation between higher education and lower birth rates has been shown time and again, so obviously the first step is educating women about birth control.  The countries today with the highest population growth are the poorest, those who are least able to shoulder the responsibility of feeding and raising healthy, well-educated children [4].

Why is biodiversity decreasing: Major causes of biodiversity loss

#1 Deforestation

The highest concentrations of biodiversity on land are in the tropical rainforests.  More than 50 percent of the world’s species are thought to exist in the tropical rainforests [5]. 

And yet, over the past 40 years, around 20 percent of the Amazon jungle has been cleared for timber, agriculture and cattle ranching and scientists estimate that another 20 percent of the trees will be felled over the next 20 years [6].

The elimination of plant life

In clear cutting of forests and clearing land for development, the roots of vegetation which hold the soil structure together are stripped and the topsoil containing nutrients critical for sustaining plant life is washed away. 

Topsoil forms from the decomposition of plant debris.  Plant litter, that is leaves, branches and the bark of trees that have fallen to the earth are broken down by earthworms and similar creatures, as well as bacteria and fungi, converting the soil into a rich humus capable of growing plants. 

When the soil is scraped, vital nutrients are lost and the soil is no longer able to provide the type of environment that allows seeds to sprout, roots to take purchase or plants to grow.  Not only do we lose the plants cleared away, but we lose the possibility of regrowth from dispersed seeds on that land.

Fragmentation of healthy animal populations

Deforestation results in the wholesale elimination not only of all plant life, but also of the animal life within its borders.  While some animals may escape by migrating, there is a high probability that they will not be suitably adapted to their new homes and be quickly preyed upon by other creatures, be poisoned or attacked by a disease to which it has no resistance, be shot by humans or starve to death. 

And if they do manage to survive, they may find no mates answering their calls. 

Too, it could very possibly be that a migrating animal’s only food source was in the obsolete ecosystem.  Some animals are entirely ecosystem-dependent for nesting, mating and rearing their young. 

For instance, the Northern Spotted Owl will only survive in the old growth forest habitat of the western United States temperate rain forest.

Even just fragmentation of an ecosystem can mean drastic change to the life that subsisted in an intact ecosystem.  Those at the edge become subject to threats that had not existed when the ecosystem was intact, like predators and different weather variations from which they may have been heretofore protected. 

An example is the wood thrush which typically nests deep within a forest.  Clearing for, say a pipeline or a road cuts a swath right through the forest, bringing the nests to the edge.  Now cowbirds surreptitiously lay their eggs in the wood thrush’s nest when the parents are out.  The parent thrushes return to the nests and dutifully warm the eggs to hatch.  Aggressive baby cowbirds push the thrush chicks tumbling to their deaths and the population of wood thrushes comes to the end of its line in the new abbreviated forest.  This really happens.

When a forest is fragmented, the number of possible sanctuaries is diminished, as well as an animal’s food sources.  The new, smaller populations are less likely to survive against stressors like disease and predation than a larger population which is more likely to contain a greater number of members who are strong enough to weather the stressors and procreate, insuring the survival of the population and sometimes even the entire species. 

And should animals try to cross the separation area, it becomes vulnerable to predator or other dangers, such as getting hit by a car.

The destruction of staggering rainforest values

The effects of the current disproportionate fragmentation of rainforests is especially worrisome. 

Rainforests do not have the species reduction pressures of most other ecosystems like weather extremes. Instead, they are very much closed systems with a high level of photosynthesis happening and fairly steady temperatures and rainfalls, resulting in the evolution of many diverse species. In fact, half of all of the species on earth. 

These species have developed elegant mutualisms for maintaining a natural balance within the dark canopied environs. 

For example, reproduction of the many fruit trees occurs not through pollination as there is not a lot of wind, but primarily through monkeys, bats and other animals eating the fruits and defecating or regurgitating seeds across the ecosystem. 

While many trees have developed toxins in their leaves to ward off chewing insects, the fungus gardener ants chew off tiny parts of leaves they have developed a resistance to and carry them underground to their colonies where they grow a fungus which is their only food source.  

The number of species in the tropical rainforests is unknown but estimates for example of over 1,000 species of butterflies in a two-kilometer area, suggest a staggering diversity. 

But realize that in deforestation or fragmentation all of these species can be swiftly wiped from the face of the earth. 

And because the mutualisms they have developed in order to maintain the balance of the ecosystem are not readily apparent, we may be destroying the underpinnings of the ecosystem itself without having had a chance to even identify key species.  Seventy percent or more of the plants we use to treat cancer today were found in tropical rainforests [7]. 

#2 Further habitat loss and nature degradation

Urban sprawl, that is, the expansion of territory used by humans for any activity demands habitat loss. 

Habitat loss generally involves development, sometimes intensive development and subsequent permanent population by humans. 

It eliminates natural habitats with one scoop of the backhoe, fragments ecosystems so they are unrecognizable as such in an afternoon, and forces migration of any animals and birds which might have survived.

These suddenly homeless animals than have to quickly figure out many crucial things for their survival, including:

• how to find safe shelter and food
• recognize and avoid parasites, pathogens and predators
• figure out how and where to find a mate
• learn to swiftly recognize and avoid human traffic in its many forms

#3 Overexploitation

The World Wildlife Fund asserts that overexploitation is the second largest threat to many species after habitat loss. 

If overfishing continues at its present rate, the world will run out of seafood by 2048 [9]. 

Overhunting is done for several different reasons, one is for the high profits to be made in the illegal wildlife trade of plants and animals.

The illegal wildlife trade is an international concern, the fifth largest contraband trade following on the heels of narcotics. 

The demand is rising for animal parts in medicine, food, amulets and other products, threatening the survival of many endangered species. And the fact that they are endangered makes the price rise even higher, meaning the profit is higher and worth the risk for the unscrupulous or hungry. 

The trade in pangolins, small shy mammals living quietly in Asia and sub-Saharan accounts for around 20 percent of all illegal wildlife trade.  An estimated 100,000 pangolins have been captured and sold every year for the past ten years, primarily for the advertised curative powers of their body parts, and their meat is considered an edible delicacy. 

Their scales alone command a price of $3,000 a kilogram on the black market and the meat is selling at $150 pound in Vietnam and China.

#4 Air pollution

Pollution, in the many forms it takes, is a major threat to biodiversity.

Air pollution can affect animals and birds through inhalation of gases or small particles, ingesting particles suspended in food or water or in the case of soft-bodied invertebrates like earthworms or animals with thin, moist skin like frogs and lizards, by absorbing gases through the skin [11].

Disappearing frogs

Frogs have been called the perfect measures for chemical pollution and climate change because amphibians are extremely sensitive to small changes in temperature and moisture. 

Accordingly, theories abound over the recent mass disappearance of amphibians and the many deformities observed, including poisoning from the noxious gases from burning fossil fuel and from the toxic chemical residue in air and waters from over-spraying agricultural fields. 

It has been questioned whether it might be the depletion of the ozone layer that was protecting their sensitive skin. 

Acid rain, which fundamentally alters the pH of their natural habitats has been suggested as well, but the current theory is that the biggest factors are habitat destruction, climate change and a fungal disease [12].

 Loss of topsoil

Acid rain contains free hydrogen atoms which bind with key chemicals in the earth’s topsoil, liberating their bonds and allowing vital nutrients to simply wash out of the soil, leaving the earth too barren to sustain life.  Loss of the earth’s topsoil is becoming a large concern as this is not something we can easily replenish. 

Topsoil is created by an ecosystem of organisms, fungi and bacteria and this is generally not a swift process or one that can be synthetically replicated.

Air pollutants affect plants as well, damaging their leaves, their ability to photosynthesize, their value as a food source and even killing them [13].  When plants or soil organisms such as earthworms that have taken the pollutants unto their tissue are eaten by animals, animals, the pollutants enter the food chain causing further injury to susceptible organs of the predator. 

Metals may affect not only the respiratory systems, but the circulatory systems, reproductive systems, gastrointestinal and central nervous systems, causing changes in birth, growth and death rates of entire populations [14].

#5 Water pollution

Water pollution decreases biological diversity as well. 

Water pollution can include:

• debris from garbage dumping, including plastic in the oceans which can strangle, suffocate or congest the gastrointestinal systems of birds and marine life;
• oil and petrochemicals from many different sources;
• heavy metals from acid mine drainage;
• debris from thousands of fishermen over recent years, like drifting nets that continue to catch fish like ghosts would, by tangling them until they die or are eaten by predators;
• garbage and chemicals from urban storm water drains;
• direct radioactive and hazardous waste;
• raw sewage.

In short, if you can imagine it, it is being disposed of in the water.

Thermal pollution from power plants and factories has also been shown to disrupt the natural balance of the species distribution and decrease biological diversity because fewer organisms in the area are able to adapt to the warmer water.  Whether it leads to decreased biological diversity is a matter of conjecture.

The growth of aquatic plant life is affected by polluted water. In addition to nibbling on fluoride-riddled plant leaves, a fish can absorb toxins just by swimming through them or can more or less deliberately eat a tasty sauce of petrochemicals floating on a blue (plastic) eel …a concoction destined to be served over and over as the flavors bio-accumulate in the fatty tissue of its predator [15]. 

The internal organs of humans are not any more fond of petrochemicals even if accompanying a meal of fresh flounder, but this may be part of the top down solution to an overpopulation of predators.

Acidic cocktail to live in

Our waters are becoming more acidic due to the deposition of the acidic particles in the air from burning fossil fuels.  This crap, chemicals rising from smokestacks and out of exhaust pipes, floats around in the air on wind currents and then comes down to earth or sea with the rain and snow. 

Water acidification has been shown to decrease egg production and embryo survival in fish, decrease fish growth, cause respiratory distress and physiological impairments and increase fish mortality [16].  And while birds and animals may not be directly affected by the alteration of acid levels in water, the disappearance of their food source definitely affects them. 

For example, many birds rely upon mollusks and other invertebrate species that retain high concentrations of calcium. 

Like humans, birds need calcium for bone growth.  Unfortunately, mollusks and many invertebrate species, like coral are decomposed by acid.

Waters devoid of all life

Nutrient pollution is unquestionably causing a decrease in biological diversity. 

Each year during the growing season, 7700 square miles or 20,000 kilometers of water at the mouth of the Mississippi River is considered a Dead Zone.  Completely dead, unable to sustain any life as we know it. 

The nutrient pollution from agricultural fertilizer runoff there causes algal blooms which deplete the marine environment of oxygen.  Nutrient overloads are also caused by the dumping of urban wastewater and nitrogen oxides from burning fossil fuels that have come down in the rain.

There are Dead Zones in oceans all over the world from nutrient pollution, some more permanent and some very large. 

Particles of nitrogen oxide, discharged from smokestacks and exhaust pipes that come down with the rain contribute a toxic amount of nitrogen to some bodies of water like Lake Erie, one of the five Great Lakes of America.

#6 Land pollution

Land pollution, like acid mine drainage, hazardous waste sites, deposition of toxic chemicals from the air, whatever the source is a special threat to biodiversity because it diminishes the land available for any plant growth. 

This is especially serious because we need arable land for growing much of the food we rely upon. 

#7 Climate change

Another major threat to biodiversity is climate change. 

Climate change is the recent rapid warming of the earth due in large part to the burning of fossil fuels which is creating too much carbon in the atmosphere. 

Rainforests have been studied for their role as a carbon sink, absorbing copious amounts of this greenhouse gas emission.  And yet, we are rapidly eliminating the rain forests.

When we do this, we are losing an invaluable resource. 

For the most part, rain forests are either logged for timber or cut and burned to be converted into pasture for farming or cattle-ranching.  Mature forests act as a carbon sink, storing carbon in wood, leaves and the soil. 

When the forest is cleared, that carbon is released. Deforestation accounts for nearly 20 percent of greenhouse gas emissions [17] and is second only to burning fossil fuels as a contributor to climate change. 

In fact, deforestation contributes more greenhouse gas emissions than the world’s entire transport sector.

Species suffer because of anthropogenic climate change

The effects of climate change on some creatures is already profound.  Animals are no longer able to live in their natural habitats because they are too warm or the water has risen too high are migrating simply to stay alive. 

The problem is that living creatures in their natural habitat are part of a natural ecosystem that is balanced and interdependent.  An oft-cited simple example is that birds rely on caterpillars for food.  Caterpillars rely on new growth leaves for food. 

If a bird is forced to a cooler climate and its chicks are born in accordance with its reproductive schedule before the caterpillars have hatched because the new buds have not erupted, then the baby chicks will starve to death. Too, the birds may not have built a resistance to diseases prevalent among its new neighbors or there may be too many predators of its eggs for the species to continue. 

There are many variables in a balanced ecosystem. 

The recent phenomenon of rapid climate change due to anthropogenic activity can fatally interrupt this synchrony at any level.  It is a simple fact that creatures have not had the time to adapt. 

Another scenario is that the plants the caterpillars rely upon may no longer be able to survive in their natural habitat due to global warming.  As we saw above with the fungus garden ants, some species rely upon a single food source.

Coral reefs, often called “the rain forests of the sea” due to the rich biological diversity living in these ecosystems are dying from the rising ocean temperatures and acidification.  Coral reefs are home to one quarter of all marine species [18].

#8 Invasive species

The ease with which one can travel the globe and the plenitude of transcontinental voyages has increased invasive species everywhere.  Climate change affords yet another advantage to invasive species that bloom earlier in an extended growing season, taking firm hold and crowding out the new growth of native species. 

Regardless of the reason for its appearance in an ecosystem, an invasive species can cause the loss of biological diversity by choking out native plants and by displacing the habitat and food source of the animals and birds who live there.

As the climate warms, invasive species are able to better take hold in areas where they bloom before native plants do in a particular area. As climate change leads to extended growing seasons in some areas, invasive plants take advantage by flowering earlier and crowding out less adaptable indigenous species.

Why is it important to preserve biodiversity?

Biodiversity strengthens the web of life and contributes to healthy ecosystems.

Healthy ecosystems provide us everything we need to survive:

• fiber for textiles
• materials for shelter
• our medicines
• food
• fuel
• energy

Healthy ecosystems contribute to clean air and climate regulation, clean water through filtration and decompose and cycle organic matter to make rich soil so that the process of life can continue.

Negative consequences of biodiversity loss

We don’t know all of the reasons for the different extinctions. 

We can examine the effects of suspected activities. For example, we don’t know why we are suffering the loss of pollinators right now.  But we do know that it is a serious matter to lose the majority of our pollinator insects performing a service we need for the production of food.

We do know that to lose a key species in an ecosystem means the collapse of the ecosystem and all it contains and represents. 

And what does a lush tropical rainforest with parrots and pineapples represent?  Will our planet miss them?  What does the loss of a wetland with frogs trilling on a fresh, summer night represent? 

The Australian Aboriginals were losing their entire creation myth with government relocation and usurpation of their waters embodying sacred places until they began asserting their rights to a government willing to listen.   

Many of the few remaining Native Americans have lost their sense of identity with the extermination of their race, the displacements, the fragmentation of their society. 

Humans are resilient and some reasonable facsimile of a human may be able to adapt to a polluted world, but it will be a very different world and it may be one that is missing some key components for a continued existence on earth.