Pollution, Environmental, Degradation & Disease

Pollution & environmental degradation

Even if habitats are structurally intact, individuals, populations, species, communities & ecosystems can be profoundly damaged

Pollution and evntal degradation - obvious causes

keeping too many cattle in a grassland community gradually damages it, often eliminating native spp. and favoring invasive spp.

Pollution and evntal degradation - causes not obvious

fishing trawlers drag ~15 million km2 of ocean floor annually, destroying delicate creatures (e.g., anemones, sponges), reducing spp. diversity & biomass and altering community structure

Pollution

• Subtle form of environmental degradation caused by:

• pesticides, herbicides, sewerage, fertilizers from agriculture, industrial chemicals & wastes, emissions from factories & automobiles, & sediment deposits from erosion

Pesticide pollution

▪History: first brought to our attention in Rachel Carsen’s influential book: Silent Spring

▪She described biomagnification, whereby pesticides such as DDT become concentrated as they ascend the food web

▪For example, pesticides are added to crops to kill insects or added to water bodies to kill mosquitos

Pesticide pollution DDT

• Animals, especially top predators such as eagles and hawks, were declining due to biomagnification after WWII, because they were eating animals exposed to DDT (dichlorodiphenyltrichloroethane)

• For example, during 1970-2000 there were no bald eagles nesting in Louisiana; now they are common in many areas

Peregrine Falcons - DDT

• Once common

• 1940s: DDT introduced to control mosquitos

• DDT>DDE = interferes w/calcium production

• Eggshells too thin, mothers crushed their own eggs

• Severe declines in PFs, bald eagles, brown pelicans & others

• 1970s: DDT banned

• 1999: PF de-listed as an Endangered Species

water pollution

• Destroys food sources, contaminates drinking water with chemicals

• Severely damages aquatic ecosystems

• Pesticides, herbicides, petroleum products, heavy metals (e.g., mercury, lead, zinc), detergents, toxic chemicals (PCB’s) and industrial wastes directly kill aquatic organisms, including fish, invertebrates, amphibians and marine mammals

• River, lakes and oceans are used as open sewers for industrial waste & residential sewerage

• More people = more water pollution

• Diffuses over a wider area than terrestrial pollution

• Biomagnification is also a problem in aquatic systems

  • Plants & animals are often adapted to filter large volumes of water in order to obtain essential minerals…

  • …but when the water is polluted they end up concentrating toxins (e.g., mercury) which can bioaccumulate in fish and effect the nervous systems of animals high in the food chain that eat fish (e.g., humans, marine mammals, eagles)

Water pollution - too much of essential minerals

• Even essential minerals that are normally beneficial become harmful pollutants at high concentrations

• For example, releases of human sewerage, agricultural fertilizers, detergents and industrial wastes add harmful levels of N & P in aquatic systems (eutrophication)

• Algal blooms from the above outcompete other planktonic species & detrimentally shade bottom-dwelling plant species

  • As the algae die and sink they cause booms in bacteria and fungi & absorb oxygen. Without oxygen, animal life perishes (e.g., visible as fishkills)

Water pollution - red tides

Red tides are algal blooms involving dinoflagellates

Can cause massive fish kills

air pollution

• Historically, people assumed that the atmosphere was so vast that the materials released would become widely dispersed with minimal effects

• Today we know that air pollution has damaged whole ecosystems and creates problems for humans as well

Acid Rain

• Produced when smelting operations and coal- and oil-fired power plants release huge quantities of nitrogen oxides & sulfur oxides in the atmosphere

• Those chemicals combine with moisture in the air to produce nitric & sulfuric acids

• These acids are incorporated into weather systems and dramatically lower the pH of rainwater (pH<5)

• Adverse impacts on forests, freshwaters, soils. Leads to the death and weakening of trees & other plants, insects & other animals over wide areas

Acid rain effects

Increased acidity (pH< 5) of freshwater systems causes invertebrates, fish and amphibians to perish, or causes them to fail to breed (e.g., eggs and tadpoles of frogs)

Increased acidity also inhibits the process of decomposition, lowering the rate of mineral recycling & ecosystem productivity

Many ponds & lakes in industrial countries have lost portions of their animal communities due to acid rain; many are in near-pristine areas hundreds of miles from sources of pollution

Acid rain – regulations lead to a solution!

• 1970s: public awareness of acid rain began

• 1980s: dismissed by President Reagan, until he visited Canadian border: damaged forests due to drifting pollution from he U.S. Midwest

• 1990s: report: 2% of New England lakes too acidic for trout; 6% for minnows

• 1990s: series of amendments to the Clean Air Act to control emission of SO2 and NO2

  • Called for 50-70% reductions in emissions over time

• By 2000s: SO2 emission reductions were ahead of their 2010 target

ozone

• an upper atmosphere gas that is “earth’s sunscreen,” protecting organisms from dangerous wavelengths of (solar) UV radiation

• Automobiles, power plants & industrial activities release hydrocarbons as waste products; in the past CFCs (chlorofluorocarbons) and halons were used extensively in refrigeration, aerosol spray cans and as propellants (e.g., fire extinguishers)

• In the presence of sunlight, these chemicals react with the atmosphere to reduce ozone

Negative effects of ozone depletion

Too much ozone?

Although ozone high in the atmosphere is important for protection from UV radiation, too much ozone at ground level damages plants (including agriculture) and animals

Toxic metals

• Lead gasoline, coal burned for heat and power, mining and smelting operations, and other industrial activities release large quantities of lead, zinc & mercury which are poisonous to plants & animals

• Lead poisoning cases are down in recent decades in many countries due to the ban on leaded gasoline and lead-based paints

lead levels over time

• unleaded gas introduced in 1970s; leaded gas banned by 1996

• lead-based paints were banned in 1978; paint on/in houses built before then likely contain lead

EPA - its creation

• In 1970, following a number of environmental problems/disasters, President Richard Nixon created the Environmental Protection Agency (EPA)

• The problems included deteriorating city air, human debris in natural areas & contaminated urban water supplies

• The EPA was tasked with improving water treatment facilities, setting air quality standards, a cleanup of facilities that fouled air & water, legislation to end dumping of wastes into the Great Lakes, taxing lead additives to gasoline & strategies for prevention and cleanup of oil spills

Superfund

• By the 1970s thousands of contaminated sites existed nationally due to hazardous waste being dumped, left out in the open, or otherwise improperly managed

  • These sites include manufacturing facilities, processing plants, landfills and mining sites

• In 1980 the EPA set up Superfund, which allowed them to clean-up the nation’s worst hazardous waste sites & respond to locally and nationally significant environmental emergencies

EPA - recent times

• The previous Trump administration dismissed or re-assigned many EPA scientists and replaced them with lobbyists

  • Regulations on industry were rolled back

• The Biden administration has dismissed many of those lobbyists in an attempt to restore the science that informs regulations

• The new Trump administration is beginning to deregulate industry including safety measures designed to prevent human fatalities and injuries

• Those genuinely interested in environment are concerned that without a science-informed EPA we will repeat the mistakes of the past with regards to polluting the environment

Pollutants do not observe political boundaries!

• Many countries have tightened regulations (e.g., the banning of leaded gasoline lead-based paints in the U.S.)

• However, pollutants can often cross borders, in both water and air, causing major issues for neighboring countries with different regulations

• Therefore, international agreements are important for the health of humans and ecosystems

Disease

• Disease can be a major threat to biodiversity

• Often grouped with invasive species effects; sometimes in its own category

• Responsible for 31 extinctions and countless extirpations & population declines

• May increase due to not only habitat loss but also environmental degradation

Chytrid fungus and amphibians

• Frogs with the invasive chytrid fungus develops chytridiomycosis which often kills them

• Degrades the keratin layer in the skin of frogs & mouthparts of tadpoles

• Interferes with breathing and nervous system function

• 9 spp. have gone extinct, 500 have exhibited declines, others mildly or not affected

White-nosed Syndrome & Bats

• White-nosed syndrome is an invasive disease caused by a cold-loving fungus

• Grows on the skin and disturbs bats during hibernation, causing dehydration, starvation and death

• First found in New York in 2006; has spread to 35 states

• Has caused >90% declines in 3 species of bats: northern long-eared bat, little brown bat, tricolored bat

Avian influenza (Bird flu) & birds

Occur naturally among >100 wild aquatic birds worldwide

• Ducks, geese, swans, gulls, terns, shorebirds, etc

Spread through saliva, nasal secretions, feces & surfaces

Can kill wild birds but some individuals & species become reservoirs

Pentastomes & reptiles

• Parasitic crustaceans that live in the lungs of snakes & other reptiles

• Eggs pass through the digestive tract of the definitive host (e.g., snake)

• Coprophagous insects ingest the eggs (e.g., roaches)

• Insectivores (e.g., lizards, frogs) become the intermediate host when they eat the insects and are infected by larvae

• Definitive host is infected when consuming the intermediate host