Ecosystem conservation
The bald eagle nearly vanished from the lower 48 states: by the 1960s, DDT had left only about 400 nesting pairs. Today there are tens of thousands of nesting pairs. It was no accident: it was the result of specific conservation decisions, including the Endangered Species Act and a ban on DDT. Understanding the threats is the first step toward reversing them. Look back at the end: what combination of measures saved the eagle?
Threats to biodiversity
Wild vertebrate populations have declined by about $70\%$ on average since 1970, and species are now going extinct at rates tens to hundreds of times the natural rate. Which human factors explain this massive loss of living things in such a short time?
Overfishing and management tools
Overfishing means catching fish faster than the population can reproduce, so the stock shrinks. Management tools give fish time to breed: closed seasons (no fishing while fish spawn), minimum size limits (young fish can grow and reproduce at least once), quotas (a cap on the total catch) and marine protected areas. Bottom trawling and bycatch cause extra damage.
Marine threats and everyday actions
The ocean faces plastic pollution (bags and microplastics that animals swallow or get tangled in), oil spills, overfishing and warming and acidifying water. Everyday actions matter too. Helping: planting native species, installing nest boxes, keeping pets from being released. Harming: releasing exotic animals, or pouring used oil down a drain, since it ends up in rivers and the ocean and can contaminate large volumes of water.
Name three current threats to biodiversity and briefly explain what one of them consists of.
Name three current threats to biodiversity and briefly explain what one of them consists of.
What is an invasive alien species? Give an example present in Spain and explain the problem it causes.
What is an invasive alien species? Give an example present in Spain and explain the problem it causes.
State whether these actions help or harm biodiversity and justify one of your answers: releasing an exotic animal into a river, planting native species, pouring used oil…
State whether these actions help or harm biodiversity and justify one of your answers: releasing an exotic animal into a river, planting native species, pouring used oil down the drain, and installing nest boxes.
Name two threats facing the marine environment and briefly explain one of them.
Name two threats facing the marine environment and briefly explain one of them.
The zebra mussel, which arrived from the Caspian region, invades Spanish rivers and displaces native species. Explain which characteristics make it an invader and why it…
The zebra mussel, which arrived from the Caspian region, invades Spanish rivers and displaces native species. Explain which characteristics make it an invader and why it is so difficult to eradicate.
Explain what overfishing is and how measures such as closed seasons or minimum catch sizes help recover fish populations.
Explain what overfishing is and how measures such as closed seasons or minimum catch sizes help recover fish populations.
A coastal community makes its living from a shellfish whose populations are overexploited. Design a management plan with two specific measures and explain how it…
A coastal community makes its living from a shellfish whose populations are overexploited. Design a management plan with two specific measures and explain how it balances the conservation of the resource with the local economy.
In situ and ex situ conservation
Laws, lists and numbers
The Endangered Species Act (ESA) protects species listed as threatened or endangered and their critical habitat. You can search the listings in the U.S. Fish and Wildlife Service's ECOS database. CITES is an international treaty that regulates trade in wild animals and plants. The IUCN Red List is a global ranking of how threatened species are; it guides conservation priorities.
Small sites can matter too: a tiny protected plot (a few square meters) can be effective when it holds the only population of a rare plant, because the species' whole habitat is inside it.
To judge a recovery plan, use percent change = (final − initial) ÷ initial × 100.
Captive breeding and reintroduction
A captive breeding program raises animals in zoos or breeding centers, often with careful pairing to keep genetic variety. Chicks or young are then reintroduced (released) into protected habitat. Reintroduction works only if the original threats are reduced, the habitat is suitable and food is available, and the animals are monitored after release.
Conservation often involves conflict, such as wolves and ranchers or a new park and local farming. Use cost-benefit thinking: list benefits and costs for each group and look for a compromise, such as compensation to ranchers for livestock losses.
What is a national park? Name one in the United States and a characteristic species or landscape that it protects.
What is a national park? Name one in the United States and a characteristic species or landscape that it protects.
What is the difference between a national park and a state park? Name an example of each, if possible from your state.
What is the difference between a national park and a state park? Name an example of each, if possible from your state.
Explain what the Red List of threatened species is and what it is for.
Explain what the Red List of threatened species is and what it is for.
What is a seed bank? Explain what it is for and why it is considered a form of ex situ conservation.
What is a seed bank? Explain what it is for and why it is considered a form of ex situ conservation.
Distinguish between in situ conservation (national parks and nature reserves) and ex situ conservation (zoos, seed banks, or germplasm banks), and state one advantage of…
Distinguish between in situ conservation (national parks and nature reserves) and ex situ conservation (zoos, seed banks, or germplasm banks), and state one advantage of each strategy.
The Iberian lynx population has grown from around 100 individuals to more than 2 000 in just two decades. Cite two conservation measures that have made this recovery…
The Iberian lynx population has grown from around 100 individuals to more than 2 000 in just two decades. Cite two conservation measures that have made this recovery possible and explain how one of them works.
Captive breeding programs have made it possible to reintroduce species such as the bearded vulture. Explain what they consist of and what must happen in the natural…
Captive breeding programs have made it possible to reintroduce species such as the bearded vulture. Explain what they consist of and what must happen in the natural environment for the reintroduction to succeed.
Flora micro-reserves protect small plots where very rare plants live. Explain why protecting an area of just a few square meters can be effective if it is home to a…
Flora micro-reserves protect small plots where very rare plants live. Explain why protecting an area of just a few square meters can be effective if it is home to a unique species.
The graph shows the change in the population count of an endangered species since its recovery plan was launched. Calculate the total percentage increase between 2010…
The graph shows the change in the population count of an endangered species since its recovery plan was launched. Calculate the total percentage increase between 2010 and 2024, describe the trend, and assess whether the recovery plan is working.
Two recovery plans give these census results between 2010 and 2020: species A goes from 40 to 90 individuals and species B from 120 to 85. Calculate the percent change…
Two recovery plans give these census results between 2010 and 2020: species A goes from 40 to 90 individuals and species B from 120 to 85. Calculate the percent change for each census, explain which plan seems to work better, and cite another piece of data you would ask for before drawing conclusions.
The presence of the wolf generates conflict with some livestock ranchers. Present two arguments in favor of its conservation and two from those who oppose it, and…
The presence of the wolf generates conflict with some livestock ranchers. Present two arguments in favor of its conservation and two from those who oppose it, and propose a compromise solution.
The creation of a national park is being considered in a county with tourism and farming. Analyze two benefits and two possible conflicts of the measure and suggest a…
The creation of a national park is being considered in a county with tourism and farming. Analyze two benefits and two possible conflicts of the measure and suggest a solution for each conflict.
Topic Challenge. How would you prevent the extinction of a key species in your area? Become an environmental consultant and prepare a reasoned conservation proposal to…
Topic Challenge. How would you prevent the extinction of a key species in your area? Become an environmental consultant and prepare a reasoned conservation proposal to halt biodiversity loss in your state.
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Official data search: Access the official U.S. Fish and Wildlife Service website (the Environmental Conservation Online System, ECOS) and select a native plant or animal species listed as threatened or endangered in your state.
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Analysis of ecosystem value: Create a data table describing its natural habitat, the human-caused pressures it faces, and the ecological services it provides (such as pollination, seed dispersal, or pest control).
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Conservation plan: Write a brief recovery report that includes $3$ realistic and well-founded measures: one for habitat restoration, another for legal or management action, and another for environmental education, estimating a timeline for implementation.
Evaluation criteria:
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Accuracy in obtaining and recording official data from the U.S. Fish and Wildlife Service.
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Understanding of the ecological value and threats to the selected species.
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Feasibility, coherence, and biological foundation of the conservation measures.
Habitat fragmentation and ecological corridors
When a road is built straight across an oak forest, the area cleared is less than $2\%$, yet years later the forest birds have disappeared from the area. Why is splitting an ecosystem into pieces far more destructive than losing a small strip of land?
Fragmentation also connects to island biogeography: an isolated fragment acts like an island. Smaller, more isolated fragments have lower immigration and higher extinction rates, so they hold fewer species. Wildlife overpasses, like the one planned over U.S. Highway 101 near Los Angeles, reconnect them.
Roads and fences divide forests into isolated fragments. Explain what habitat fragmentation is and why small, isolated populations are at greater risk of disappearing.
Roads and fences divide forests into isolated fragments. Explain what habitat fragmentation is and why small, isolated populations are at greater risk of disappearing.
Wildlife crossings, such as overpasses covered with vegetation over highways, allow animals to cross roads. Explain what problem they solve and relate it to the…
Wildlife crossings, such as overpasses covered with vegetation over highways, allow animals to cross roads. Explain what problem they solve and relate it to the connection between populations.
The construction of a highway has split a protected natural area in two, leaving a population of badgers separated into two isolated groves. Over the years,…
The construction of a highway has split a protected natural area in two, leaving a population of badgers separated into two isolated groves. Over the years, environmental officers detect an increase in inbreeding, a lower birth rate, and frequent roadkill of individuals attempting to cross the road.
- a) Justify why the isolation of these populations threatens their long-term survival, even though the original forest remains well-conserved.
- b) Design a proposal based on wildlife corridors to restore connectivity between both sectors without halting highway traffic, and predict what benefits this measure will bring to the species' migrations and genetic exchange.
One Health: environment, animals and people
Human health, the health of other animals and the health of ecosystems are connected: this is the One Health approach. Contaminated water, habitat loss or antimicrobial resistance do not respect the separation between these areas.
A city council is planning to build a parking lot next to a lagoon where protected birds overwinter. Draft a set of arguments outlining two foreseeable impacts of the…
A city council is planning to build a parking lot next to a lagoon where protected birds overwinter. Draft a set of arguments outlining two foreseeable impacts of the construction work and two less harmful alternatives.
Exotic parrots and tortoises are offered on an internet website without official documentation or a CITES certificate. The seller states in the advertisement: "Buying…
Exotic parrots and tortoises are offered on an internet website without official documentation or a CITES certificate. The seller states in the advertisement: "Buying these animals does not harm nature because in captivity they live better protected; moreover, if you ever get tired of them, releasing them in the countryside of your state will help enrich local biodiversity".
- a) Refute the seller's claims by justifying two severe ecological impacts caused by the illegal capture of these species in their native ecosystems.
- b) Predict what unforeseen consequences native wildlife could suffer if a buyer decided to release one of these exotic specimens into a nearby natural environment.
- c) Design two responsible and specific courses of action that any informed citizen should follow if they detect a similar situation.