Lecture 21 + 22 Flashcards
Which of the following is the biggest pool of nitrogen on earth?
Nitrogen in the atmosphere
Nitrogen fixation involves
A process where N2 is converted to a form usable by plants
In the amphibian disease example in your book… Amphibian disease may be related to fertilizer production because?
Fertilizer enhances an intermediate host of a frog parasite
Biodiversity and nitrogen cycle are
way past the tipping point
Less nitrous oxide (N2O) than CO2 or methane in atmosphere
- rate of increase is less
- but, nitrous oxide is even more potent as a ghg per mass (200-fold greater than CO2; 2-fold greater than methane)
- is the 3rd most important gas behind current greenhouse warming
- AND, holes in the ozone layer!
Remember: 99.9% or more of nitrogen on Earth is N2.
Prior to human intervention, only bacterial N fixation could make this nitrogen biologically available
Fritz Haber discovered a way to make synthetic nitrogen fertilizer from atmospheric N2 gas in 1909
Today, this literally feeds the world!
80% of the nitrogen that supports food production comes from this industrial process (and 80% of the nitrogen in your proteins, if you eat like an average person)
Fritz Haber –lessons to consider
- brilliant scientist
- changed world agriculture forever, hugely increasing productivity
- starvation and malnutrition decreased
- global population boom in response
- won Nobel Prize for his nitrogen work
- also a MAJOR player in developing and applying chemical gas weapons in WWI
- today, widely considered a war criminal (although never tried or convicted)
Greenhouse gas warming is not the major problem with human alteration of the nitrogen cycle
Rather, creation of reactive, biologically available forms of nitrogen that cause acidification and fertilization, with multiple ecological (and human health) ramifications
CO2 and methane are almost uniformly distributed on Earth, so alteration of their cycles is truly global
For nitrogen, alteration of cycle is not of N2 (too ubiquitous!), but rather of reactive, biologically available forms of N
Huge regional and local variation, since reactive nitrogen (nitrate, ammonium) tends to cycle at scales of 10s of metres to hundreds of kilometres
Regions of greatest nitrogen were once limited mainly to Europe and North America. But as new economies develop and agricultural trends shift, patterns in the distribution of nitrogen are changing rapidly.
Recent growth rates in nitrogen are changing rapidly. Recent growth rates in nitrogen use are now much higher in Asia and in Latin America, whereas other regions – including much of Africa –suffer from fertilizer shortages
Southern Brazil
Rapid population growth and industrialization around Sao Paulo, poor civic sewage treatment and vibrant sugar cane production all contribute to this new South American nitrogen hotspot
East and South Asia
More vigorous application of fertilizer has produced stunning increases in maize and wheat production, but China now has the highest fertilizer inputs in the world
So while humans have doubled the rate of creation of reactive nitrogen across the terrestrial biosphere
the increase has been 20-fold in some regions with almost no change in others
Environmental consequences of accelerated N cycle
- coastal eutrophication and “dead zones”
- loss of biodiversity in forests, wetlands, grasslands, etc.
- acid rain: damage to waters and soils
- damage to growth of forests and agriculture, due to ozone pollution (reactive N in atmosphere + methane or other organic molecules = ozone)
- global warming and stratosphere ozone holes from N2O
Nitrogen is the biggest pollution problem in coastal marine ecosystems
Phosphorus is a bigger problem in freshwater lakes
Step 1 of process of eutrophication
Farmers apply fertilizer or manure to their crops
Step 2 of process of eutrophication
N enters small waterways via runoff or leaching
Step 3 of process of eutrophication
N from entire watersheds enters estuaries and oceans
Step 4 of process of eutrophication
Because N is limiting for most photosynthesizers in oceans, their populations grow
Step 5 of process of eutrophication
There are large phytoplankton (algal) blooms
Step 6 of process of eutrophication
Many phytoplankton die and sink out of the surface waters into deeper waters
Step 7 of process of eutrophication
Dead phytoplankton are consumed by decomposers
Step 8 of process of eutrophication
The amount of oxygen in the bottom water declines
Step 9 of process of eutrophication
Fish and other macroinvertebrates have reduced fitness
Step 10 of process of eutrophication
There is now a “dead zone”
Direct pollution effects of nitrogen and human health
- heart disease and lung diseases (from gases and particles in air, including ozone and fine particles)
- cancer (nitrogen in drinking water)
Indirect pollution effects (from fertilization!) of nitrogen and human health
- pollen and allergies (R-strategists)
- animals that carry diseases (mosquitoes, snails) such as malaria and schistosomiasis
Amphibian infection from parasites and nutrient levels
Low parasite input level: more infections in high nutrients (around 3:1)
High parasite input level: more infections in high nutrients (around 15:7)
As of 1990s, nitrogen pollution was viewed by the UN and International Council of Science as
THE most immediate challenge of global change (climate change was a more distant worry)
Ecologists and oceanographers from around the world
May 1993 Block Island, RI: Offseason for tourists (cold), no cell phones, no internet, no distractions.
Total focus on a simple question: “What are the inputs to and consequences of nitrogen to the North Atlantic Ocean?”
NANI
Net anthropogenic N inputs
Nitrogen under human control under the landscape is come from four sources
- NOy deposition: fossil fuel combustion, from atmosphere into ground (acid rain)
- Fertilizer
- N fixation by crops
- Net import (+) or export in foods
-> doesn’t matter which is more important, it’s the sum that matters
Strong linear relationship
More nitrogen in, more nitrogen out
Nitrogen inputs changed over time
Low in the early sixties
Mid to late eighties, much higher from central to Eastern US
150 watersheds in Europe and the US formula
Y = 0.24x + 66.5
Slope: the fraction of nitrogen that goes into landscape that comes out into rivers (24%)
-> about 25% anywhere you go in the world
-> really dry, 15%; really wet, 35%
-> rivers then goes into coastal oceans
Other 75%, not sure where it goes
- we think it’s largely denitrified and goes back to N2, produces nitrous oxide, ghg, etc.
Intercept: how much nitrogen is coming into rivers without human input, 66.5 kg
- not zero because of natural nitrogen fixation; always some natural flux
Technical solutions for nitrogen pollution exist
These are often affordable and effective
But they are often not used
Corn is a particularly leaky crop for nitrogen
Tile drains and bare fields in winter aggravate this
Ways we can do better, even with corn
- apply fertilizer in spring rather than fall: reduces N loss by 30% to 40%
- winter cover crops: reduces N loss by 3-fold
- perennial crops (grasses) rather than annuals (corn/soybean): reduces N loss by 30- to 50- fold
Human diet and the nitrogen cycle
Consider efficiencies of eating vegetable diet (based on primary producers) vs. diet that includes herbivores (beef, etc.)
Transfer efficiency of corn to cows
CE: 20%; 80% of biomass never consumed by cows
AE: 60%
PE: 5%
Less than 1% of corn grown goes to cows
- crop part of corn, 3% of energy of harvest corn
Daily average meat consumption per person
US (1952): 0.25 lbs
US (now): 0.45 lbs
World: 0.25 lbs
East Asia: 0.3 lbs
Sub-Sahara Africa: 0.07 lbs
South Asia: 0.05
So what does how much meat we eat have to do with nitrogen?
Synthetic nitrogen fertilizer is the major change in global nitrogen cycle
- for equal quantities of grains and beef, 30-times more nitrogen fertilizer needed for the beef because of the trophic efficiency
If everyone in the US switched to a Mediterranean diet
The US would use less than 1/2 as much synthetic nitrogen fertilizer, and would produce less than 40% as much manure
Before the widespread use of synthetic nitrogen fertilizer, farmers depended on return of animal manure to crop fields
Synthetic fertilizer was so cheap, it freed them of manure.
Beginning in the 1960s and rapidly expanding in the 1970s, a spatial segregation began –harvested crops began to be moved long distances, making return of manure to the field uneconomical
Manure became (and remains) a waste product and not a resource
Around 20% of synthetic fertilizer leaves field as water pollution (before biofuels boom)
Around 57% harvested in crops, the rest is probably denitrified
- some of it leaves the country
some of it’s used directly in human consumption from the crop, but most of it is not
- most is fed to animals
Global increase in ethanol biofuel driven by
increased production in the US, and based on corn
In recent years, ethanol from corn has made up approximately 0.8% of energy use in the US. What percentage of the US corn harvest went to produce this ethanol?
Approximately 40%
2009: National goal to reduce nitrogen pollution down Mississippi River by 45% to limit size of dead zone
- models predicted ethanol policies would increase nitrogen pollution by 40%
- combined with pro-active policies on farms, basically no net change since 2009
The greatest contribution to the total human input of nitrogen per year in is __________.
Manufacturing of synthetic fertilizer
True or false: Anthropogenic nitrogen additions in aquatic systems often leads to oligotrophic waters.
False. This results in eutrophic waters and even dead zones.
Which element tends to be most limiting in agricultural systems.
Nitrogen (N)
True or false: Eating less meat could help reduce problems associated with nitrogen pollution.
True
What is the order of potency of the nitrous oxide, methane, and carbon dioxide per mass from high to low?
NO2, CH4, CO2
True or false: The western United States has higher Net Anthropogenic N Input (NANI) than the eastern United States.
False. The eastern US has higher NANI.
What are viable mechanisms for reducing nitrogen pollution?
- applying fertilizer in spring rather than fall
- use winter cover crops
- use perennial instead of annual crops
- changes in human diet
What umbrella term is used to describe the various actions taken to slow down or reverse the loss of species and biodiversity?
Conservation
The term biodiversity can include?
- species richness
- genetic diversity
- community types
- all of the above
All of the above
What is the total number of Earth’s species that have been identified?
1.8 million species
Which areas of the earth are experiencing the greatest gross forest cover loss?
Boreal forests
It is documented that some introduced species can assimilate into communities without an obvious effect. However, many have caused significant alterations to native communities. Which of the following is an example of an accidentally introduced species that has reduced biodiversity?
- Finches on to the Galapagos Islands
- Tasmanian devils on to Australia
- Brown tree snakes on to Guam
- All of the above
Brown tree snakes on to Guam
Which organization established globally recognized categories of protected areas?
International Union for the Conservation of Nature
Protected areas such as _________, are large unmodified or slightly modified areas, that retain their natural character and influence without permanent or significant human habitation, that are protected and managed to preserve their natural condition, but also provide a foundation for environmentally and culturally compatible, spiritual, scientific, educational, recreational, and visitor opportunities.
- Wilderness areas
- National parks
- National monuments
- Strict nature reserves
National parks
A marine protected area is ___________.
All or mostly marine area, sometimes with portions of adjacent land
Rate of extinction
An important lesson from the fossil record is that the vast majority of species eventually become extinct – more than 99% of species that ever existed are now no longer on the planet
Extinction rates in the distant past
For every thousand mammal species, less than one went extinct every millennium (0.01% per century)
Extinction rates in the recent past
Current extinction rate is up to one thousand times higher than the fossil record
0.1% per decade
Extinction rates in the future
Projected future extinction rate is more than ten times higher than current rate
10% per decade
Endangered species
in danger of extinction throughout all or a significant portion of its range
Threatened species
likely to become endangered in the foreseeable future throughout all or a significant portion of its range, unless steps taken to better protect
Top 10 most endangered animals species on Earth
- Vaguita (small marine mammal)
- Amur leopard
- Javan rhinoceros
- Northern sportive lemur
- Western lowland gorills
- Saola (Asian “unicorn”)
- Leatherback sea turtle
- Tiger
- Chinese giant salamander
- Ivory-billed woodpecker
Passenger pigeon example
- most abundant bird ever known
- enormous flocks reported in mid 1800s
- dispersal agent of seeds such as oaks
- precipitous declines due to commercial hunting (and habitat loss)
- extinct 1913
One major cause of extinction
Over-exploitation
- over-hunting, over-harvesting
Over-exploitation American bison (buffalo) example
Could buy a trip on luxury coach with a gun and shoot the animals until you were out of bullets/barrel became too hot.
- buffalo almost became extinct
- estimated 60 million roamed Great Plains around 1800
- killed primarily for hides and for “sport”
- by 1889, 541 remained
- today, ~ 31,000 in wild populations
10 most endangered plant species on Earth
- Western prairie fringed orchid
- Rafflesia flower
- Georgia aster
- Wiggin’s acalypha
- Texas wild rice
- Howell’s spectacular thelypody
- Stenogyne kanehoana
- Ouachita mountain goldenrod
- Enrubio
- Arizona agave
Why are small populations are vulnerable
For both genetic reasons and due to environmental uncertainty at smaller spatial scales
North Atlantic Right Whale example
- slow and docile, the “right” whale to hunt (1800s into 1900s) because they float when killed
- most endangered whale on the planet
- today less than 350, with less than breeding females
- now protected from hunting, but many killed from collisions with ships and entanglement with fishing gear
African elephant example
- endangered, with 10 million in early 20th century, some 415,000 today
- demand for ivory one big problem
- ivory trade now illegal, but poaching and illegal trade persist
For island biogeography, “extinction” means
Local extinction of the population
- but of course, if that is the only population for the species, the species goes globally extinct
Should hunting of endangered or threatened species be allowed if it generates revenue for, and promotes conservation of, the species being hunted? (to protect against poaching, or protect habitat loss)
A closer look at trophy hunting: industry employs few people, money from hunt fees barely trickles down to villages, government corruption, hasn’t stopped poaching –especially in countries that have a poor record of protecting their wildlife
Heath hen example
- once extremely common from Maine to Virginia, was highly edible, easy to shoot, susceptible to introduced cats, and affected by conversion of its grassland habitat to farmland
- by 1830, it had disappeared from the mainland and was found only on the island of Martha’s Vineyard, off Cape Cod, MA
- in 1908, a reserve was established for the remaining 50 birds, and by 1915, the population had increased to several thousand
- 1916 was a bad year – fire eliminated much of the breeding ground, there was a particularly hard winter coupled with an influx of predatory goshawks, and finally poultry disease arrived
- of the 13 birds remaining in 1928, only two were females; a single bird was left in 1930, and the species went extinct in 1932
Which of the following has been most damaging to biodiversity?
- global warming
- habitat loss
- overexploitation
- ocean acidification
- ozone hole
Habitat loss
- much of this is direct disturbance (agriculture, urban/suburban sprawl), but remember nitrogen pollution
Human activity now uses somewhere in the range of
20%-40% of global net primary productivity in terrestrial ecosystems
Habitat loss has been and continues to be the largest threat to biodiversity. Many other major risks as well though, including
invasive species and infectious diseases
- increasingly, and moving forward into the future, global climate change and climatic disruption likely to have tremendous consequences on biodiversity
One approach to addressing threat of habitat loss:
Protected Areas to conserve important habitat
Protected areas
Places managed for the long term conservation of nature, often to protect biodiversity or particular species, or for cultural reasons, or scenic beauty
- various kinds (national parks, nature reserves, sites of special scientific interest) grew in both number and area during the 20th century
Is a greater proportion of land or oceans in a protected status?
Land
- Currently, about 13% of the world’s land area is “protected”
- A little over 1% of ocean area (mostly coastal) is “protected”
Protected areas try to meet many goals
- conservation of biodiversity
- conservation of a particular species
- educational uses
- recreational uses
- natural resource exploitation (lumber, fish, oil & gas)
These goals often conflict with one another
True or false: The global expansion in protected areas has worked well to preserve biodiversity
False. Biodiversity globally has continued to go down despite more area covered by protected areas.
And coral area and health continue to decline, despite corals being the focus of many marine protected areas.
Most protected areas (marine, terrestrial) are
NOT where biodiversity is greatest
- many PAs in western Europe despite it not being a diversity hot spot
- many hotspots in southeast Asia with a comparative lack of PAs
Another problem (particularly for marine areas)
For marine protected areas, less than 10% offer sufficient protection against damage from commercial fishing, tourism, etc.
What do we mean by “sufficient protection?”
A no-take (no fishing) marine protected area needs to be more than 10 times the area of a fish species’ home range, to adequately protect that fish species.
30% of the world’s no-take marine protected areas are too small to help conserve fish species that grow to 20 cm in length or more
The good news: Those marine protected areas that are truly protective are hugely effective and important
More good news. In March 2023, UN negotiators agreed on final language for a treaty on ocean biodiversity.
If enacted by majority of world’s countries, will create new marine protected areas covering 30% of the world ocean area by 2030. Focus on open ocean areas beyond territorial boundaries, a region now subject to very little protection or oversight.
Marine Protected Areas are focused on local protection of resources and provide little protection against global and regional threats.
Global change poses high risk to many coastal ecosystems (ocean acidification, “bleaching” of corals from heat)
Regional-scale nitrogen pollution can lead to eutrophication, dead zones, and loss of biodiversity and fishery resources at scales much larger than those of most Protected Areas
Success in conservation takes good scientific information, and continual diligence. Case study of North Atlantic Right Whale: < 350 as of 2022
“Large” numbers near Boston and Cape Cod.
Stellwagen Bank Marine Protected Area (Massachusetts): 2,500 large ships per year
-> changed shipping lane since 2017
Unfortunately, population has been declining again since 2020. One reason: far more ship traffic along northeast US coast as Covid disrupted global supply chains.
True or false: The rate of extinction of species is the most rapid it has been over the past several million years.
True
Threats to biodiversity
- invasive species
- habitat disruption or destruction
- overexploitation
- global environmental change
What remains the most likely cause of biodiversity loss?
Habitat loss
In which ways do human activities disrupt habitats?
- The habitat can be destroyed for development
- The habitat can be degraded by pollution
- The habitat can be altered by climate change
- The habitat can be converted to agricultural lands
You have been studying a very small population of Tasmanian Devils. What uncertainties about this small population should be of extreme importance and interest to you when prioritizing your research? (You may choose one or more answers.)
- The number of individuals born male or female
- The number of individuals that die or reproduce in a given year
- When the species evolved
- The genetic diversity of individuals in the population
- The number of individuals born male or female
- The number of individuals that die or reproduce in a given year
- The genetic diversity of individuals in the population
Which of the following are explanations as to how a species may be introduced to a new habitat?
- They were accidentally transported from one country to another during a delivery of exported goods
- They were stocked in a persons private pond to prey upon pests
- They were placed intentionally to provide a recreational opportunity
- They were imported to produce a new agricultural product
- They were accidentally transported from one country to another during a delivery of exported goods
- They were stocked in a persons private pond to prey upon pests
- They were placed intentionally to provide a recreational opportunity
- They were imported to produce a new agricultural product
You and your friend see a local news report that claims a species of coral is going to be driven extinct by ocean acidification that results from global warming. Your friend claims “That news story is just an example of sensationalism. Furthermore, it is just one species, and so it’s not that big of a deal.” What is the best response you can make to your friend?
- “I agree. It’s just one species and the earth has hundreds of billions of other species.”
- “I agree. It is sensational. Global warming is happening so slowly that species are not even really in any danger. They can all simply adapt to higher temperatures.”
- “I disagree. Communities are complex, if one species goes extinct we do not know about the wider influence on the entire community and ecosystem.”
- “I agree. Coral is really just rocks, so in reality non-living things cannot go extinct.”
“I disagree. Communities are complex, if one species goes extinct we do not know about the wider influence on the entire community and ecosystem.”
Which of the following is a reason why marine protected areas sometimes do a poor job of protecting species.
- Marine protected areas are not always in areas of high biodiversity.
- Protecting a local area does not protect from large scale problems like global warming and nitrogen pollution.
- In some areas the protections are not well enforced.
- Marine protected areas are sometimes too small.
- Marine protected areas are not always in areas of high biodiversity.
- Protecting a local area does not protect from large scale problems like global warming and nitrogen pollution.
- In some areas the protections are not well enforced.
- Marine protected areas are sometimes too small.
