How are the growing number of humans on planet Earth affecting each of the following?

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1. Habitats / biodiversity -

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2. The atmosphere –

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3. The freshwater –

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3. The oceans –

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Destroying habitats which

causes loss of species & decreased biodiversity

High emissions from industry &

transportation causes acid rain, smog, & global warming

Runoff contaminated with

surface pollutants gets into our surface & groundwater

Pollutants from land make their way

into our oceans via rivers. Acid rain is changing the pH of our oceans. Global warming is causing sea level rise.

12 Dec 2025

HUMAN IMPACT

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• However, we can look deeper into the diversity of different types of areas...
• Biodiversity of the biosphere
• All the species on Earth
• …biome
• All species in similar areas on Earth
• …ecosystem/community
• All species in a smaller area on Earth
• …population
• All the individuals of one species in an area on Earth

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Genetic Diversity

• The total number of genetic characteristics in a given population
• These variations serve as a way for a population to adapt to changing environment.
• Greater variation increases the chance that some individuals of that population will possess variations that are suited to the new environment.
• They’ll live and pass on those traits to the next generation, preventing extinction of their species!

Imagine:

• One individual has a mutation that makes it darker color than the rest of the population.
• After a volcanic eruption, so the cover is no longer pale yellow, but dark.
• The darker individual will then survive in the new environment and reproduce more than the other individuals, passing on “dark color” genes to the next generation.

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Loss of Biodiversity

• The greatest threat to biodiversity is habitat loss.

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• Habitats (places where organisms live) are “lost” due to land use changes
• Agriculture
• Urbanization

Habitat Fragmentation

• Fragmentation is the process that divides large ecosystems into smaller, isolated parts.
• As a habitat gets smaller, more and more species are affected.
• Smaller habitats -> less diversity -> less of a chance to recover from changes in the ecosystem

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Habitat Alteration

• As the human population grows, habitats are altered

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How many sunflowers

do you see?

How many could grow here?

(limited or unlimited)

Limited by what??

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What about limits here?

And here …

Each environment can only support a specific amount of organisms.

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Carrying Capacity - the largest population that a given environment can support

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Limiting Factor - An environmental factor that prevents a population from increasing

(for example: food, space, water …)

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How Do Populations Change in Size?

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Biotic potential - the maximum growth rate for a population if all conditions were ideal (plenty of food, no competition, no predation, etc)

This causes exponential growth that results in a J-shaped curve.

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What Limits Population Growth?

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Limiting resources - resources that limit the growth of a population.

For animals, these include food, water, shelter, and nesting sites.

For plants, water, sunlight and certain nutrients in the soil.

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The combined effect of all factors that limit population growth is called environmental resistance.

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The population eventually ceases to grow as it reaches (and even goes beyond) a size known as its carrying capacity.

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This is the maximum population size that an environment can support for a long period of time.

What relationship is portrayed in this graph?

DESCRIBE what you see in the graph that supports your answer.

15 Dec 2025

The prey population rises first, followed by a rise in the predator population. Then the predator begins killing off the prey organisms at a fast rate and their population crashes. This causes the predators to starve & their population crashes … which allows the prey population to rise again and the whole cycle repeats.

EXTINCTION – disappearance of ALL members of a species from ANYWHERE on Earth.

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• Species in danger of becoming extinct are classifies as Endangered.

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• Species that are close to being endangered are classified as Threatened.

WHAT CAUSES EXTINCTIONS?

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Habitat destruction

Invasive species

Population (human)

Pollution

Climate change

Overharvesting

C

So ….. How do we protect biodiversity?

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1. Captive Breeding – mating of organisms kept in zoos or wildlife preserves (ex. California Condor), but $$

2. Laws & Treaties –

• protect individual species in US with Endangered Species Act
• Protect many species from international trade with CITES (80 nations)

3. Habitat Preservation

• The most effective way
• Save/preserve the habitat & this protects the targeted species (as well as others)
• for ex. our National Park Systems

Overharvesting

• Overharvesting is the catching or removing from a population more organisms than the population can replace

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Overharvesting: Plants

• Long leaf pine and white cedar forests were decimated in our state for the lumber industry.

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Overharvesting: Animals

• Market hunting (commercial hunting) at the turn of the century exploited natural resources for profit.
• For instance, beaver were completely exterpated from the state, river otters were no where to be found in the western part of our state, it's estimated that only 10,000 deer were left, very few wild turkey were left, and black bear were found only in the deepest mountain valleys or thickets in Pocosins near the coast.

Invasive Species

• Native species
• Organisms that naturally live in a certain area.
• Evolved in that area over time
• Typically co-evolved with other species that keep its population in check through predation, competition or disease.
• Non-native species (invasive, exotic or alien species)
• Organisms introduced or moved to an area by humans where they don’t naturally occur.
• Not necessarily harmful…
• Harmful ones are called invasive species
• Outcompete native species in a natural community or cause ecological or economic problems
• No natural controls to limit their population
• Typically have a high rate of reproduction and tolerate a large variety of conditions
• Take over!

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Numbers so low that

the species is at risk

of extinction

Species that isn’t native to an area, but has come in and taken over

Has a very limited diet (only eats small

variety of things)

Has a wide variety

of food sources

that can be eaten

Can only live in a certain type of conditions, in a very small area

Can live in any conditions, in a wide variety of areas

Don’t reproduce often and only have a small number of offspring

Reproduce often and have a large number of offspring each time

16 Dec 2025

WHAT ARE THE EFFECTS

OF A GROWING HUMAN POPULATION ON AIR QUALITY?

Air pollution can come from natural sources such as:

• volcanic eruptions (soot, ash & sulfuric gases)
• lightning
• forest fires

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However, most pollutants come from human activities. These pollutants affect the health of humans and other living things. They can also lead to planetary changes in climate.

SMOG:

This brownish haze formed when certain gases in the air react with sunlight (aka photochemical smog)

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Major sources are gases emitted by automobiles & trucks. Gases react in sunlight and produce ozone (O₃), which is toxic and a major chemical in smog.

Thermal Inversion:

Pollutants usually blow away. As air near surface warms, it rises & carries pollutants with it … away from humans.

Sometimes a warm upper layer of air can trap pollutants at the surface.

ACID RAINS:

Powerplants & factories emit nitrogen and sulfur oxides when coal/oil are burned.

• Gases mix with water vapor
• Form nitric acid & sulfuric acid
• Fall as acid precipitation

Results in:

• Decreased pH of soil
• Destroys vegetation (trees & leaves)
• Changes pH of rivers, lakes & oceans

Indoor Air Pollution:

This is particularly a problem in developed countries because –

• Increased time spent indoors
• Tightly insulated buildings & homes

Common pollutants include:

2. asbestos – used as insulation
3. Carbon monoxide – results from malfunctioning gas heating exhaust
4. radon – radioactive gas in soil & rocks below homes

Sick Building Syndrome:

As a result of energy efficient homes, toxic substances build up & accumulate. There is no exchange of air to “flush out” contaminants.

This results in buildings where a significant number of people experience symptoms such as headaches, nausea, eye & throat irritation, etc.

Perhaps the greatest human caused effect on the atmosphere is our excessive production of CO₂ since the Industrial Revolution.

This leads to exaggerated greenhouse effect which warms Earth more than it normally should.

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Consequences include:

• Melting polar ice caps
• Glacial melting
• Permafrost thaw
• Changed precipitation patterns
• Sea level rise

• Heat waves
• Cold spells
• Increase in storm intensity
• Altered ocean currents

Is there anything that can be done?

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Kyoto Protocol (1997)

Meeting of industrialized nations in Kyoto, Japan to attempt to reduce CO₂

emissions back to the 1990 levels.

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190 countries have signed.

United States and Australia are the

only developed countries that refused.

IPCC – Intergovernmental Panel on Climate Change was established in 1988 to provide an objective source of information on climate change. It consists of hundreds of climate scientists from around the world.

• The most recent report states “Human interference with the climate system is occurring and climate change poses risks for human and natural systems”
• IPCC shared the 2007 Nobel Peace Prize for their work on climate change.

Paris Agreement – 2015 UN Climate Change Conference held in Paris, France.

• Significant because the two largest carbon emitters (China & USA) agreed to participate and sign the agreement.
• 174 countries sign to limit warming to 1.5^o C.
• Target of zero emissions by around 2030-2050.

Explain each of the following:

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1. Thermal Inversion –

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2. Sick Building Syndrome –

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A warm layer of air traps air with harmful pollutants at ground level. Can lead to mass illness and even deaths, if severe enough.

Well-insulated buildings prevent air circulating with fresh outside air. This traps pollutants inside the building and, if severe, results in illness to those working or living inside.

17 Dec 2025

Most water on Earth (97%) is saltwater.

• ¾ of remaining water (freshwater) is frozen
• Most freshwater is located far away from majority of people that need it
• ½ of US population uses groundwater

Water shortages occur when water is used faster than it is replaced. This is most common during a drought .

(period when less water than normal falls in an area)

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As global populations grow, water shortages are becoming more and more severe. Countries are forced to find alternative sources.

Ex – Saudi Arabia removes salt from seawater

WATER POLLUTION:

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Most is as a result of Human Activities, such as mining, industry, construction, and agriculture.

1. Industry & Mining:

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Chemical plants, paper & textile mills and factories that use metals have potential to pollute our waterways.

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Mining operations often release metal and sulfur wastes into our waterways.

2. Construction:

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Loose sediments mix with water running over the bare ground and end up in nearby streams & rivers. This can disrupt food sources and nesting sites of aquatic organisms.

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These sediments also reduce clarity of the water which affects the ability of aquatic plants to support the bottom of the food chain.

3. Heat:

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Factories & powerplants can release water that is used to cool machinery. If it is too hot, it raises the overall temperature of the stream and lowers the dissolved oxygen in the water, which kills fish.

4. Agriculture:

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Wastes from livestock & farm chemicals enter our waterways.

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• Fertilizers - provide nutrients to help crops grow better. Overuse leads to excess washing into streams and lead to an increase in algae. This lowers the oxygen content and kills fish.

• Pesticides – chemicals that kill organisms that can potentially destroy crops. Most sprays miss the target organism and end up in our waterways affecting other organisms.

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Fertilizers & pesticides play an important role in modern global food production – also known as Industrial Agriculture.

1. Put the following terms in order from least to worst:
1. endangered
2. extinction
3. threatened

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2. What are the leading causes for

species loss?

18 Dec 2025

Least =

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Worst =

threatened

endangered

extinction

1. How many people live on planet Earth today?

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1. Which country has the most people?
2. How many?
3. Which country recently lost the lead spot?

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5. The United States is in third place. How many people live here?

8.1 billion

India

1.440 billion

China - due to India’s higher birth rate

(population= 1.425 billion)

0.34 billion

(341.6 million)

19 Dec 2025

Currently the world’s farmers grow enough grain to feed 8 billion people …. Plenty of food.

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Then, why are people still starving???

• food is not evenly distributed
• ~ 40% of all grain is used to feed poultry & livestock

HOW WILL WE FEED 9 BILLION??

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• Put more land into crop production
• Improve crop yields
• Reduce meat consumption

Green Revolution:

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Implementation of a variety of new farming techniques in 1950’s – 1970’s that dramatically increased food production.

Mechanization:

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• Use of machines (increased fossil fuels) to replace humans and animals on farms.

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• Leads the shift toward single crop farms rather than many crops.

Irrigation:

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• Bringing water where it won’t naturally flow
• Can increase crop yields
• Enables crops to grow where they previously couldn’t grow

Fertilizers:

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• Needed to replace large quantities of nutrients
• Can be organic (animal manure)
• Can be synthetic (produced by industry)

Monocropping:

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• Both mechanization & synthetic fertilizers encourage the shift to single crop farms.

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Advantages Disadvantages

• Increases productivity

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• Increases efficiency

• Increases erosion

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• Increases disease

Pesticides:

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• Pesticide use often increases due to monocropping & has become routine in agribusiness.
• US accounts for 1/3 of global pesticide use.
• As pest populations develop resistance to pesticides, stronger pesticides must be created.

Genetic engineering:

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• Science now has the ability to alter genetic make-up of plants and to create genetically modified organisms (GMOs).
• This could increase crop yields.

Advantages Disadvantages

• Increases yields

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• Increases pesticides

• Decreases biodiversity

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• Unknown

long-term effects

Sustainable Agriculture:

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Fulfills need for food while maintaining quality of soil & minimizes use of renewable resources.

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1. Intercropping: planting 2 or more crops in the same field at same time

2. Crop rotation: rotate crop species in a field from season to season

3. Agroforestry: intercropping trees with vegetables (trees = windbreaks)

4. Contour plowing: plowing with the natural topography of the land (prevents water erosion)

5. no-till agriculture:

injects seeds into the

ground rather than

plowing fields

6. Aquaculture: farming of aquatic organisms such as fish, shellfish, & even seaweed.

• Almost all catfish & trout in US
• ½ of US shrimp & salmon

7. Sustainable fishing: allowing fish populations repopulate rather than overfish to the point of fishery collapse.

THERE IS NO ONE SOLUTION ….

REQUIRES MANY TECHNIQUES WORKING TOGETHER.

What do you THINK is meant by the term Green Revolution?

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What are some of these techniques?

The development of many new farming techniques in the 1950s-1970s that dramatically increased the production of food.

Mechanization – use of machines to farm

Irrigation – ability to grow food in new dry areas

Fertilizers – ability to grow food in nutrient-poor soils

Monocropping – single crop farms produce more food

Pesticides – prevent crop destruction by pests

Genetic engineering – ability to custom design crops

that can withstand specific area conditions

5 Jan 2026

SOLID WASTE

There are over 300 million people living in the US (less than 5% of global population) yet we generate 25% of the world’s waste!

Waste produced in homes, businesses, schools and other community places is called Municipal Solid Waste (MSW).

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Waste also comes from construction sites, industrial sites, agricultural & mining locations, but these are processed differently.

3 Methods of handling MSW are:

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1. Bury It (landfills)
2. Burn It (incinerator)
3. Recycle It

Landfills:

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• Improvement over open dumps (banned in US in 1976), but still involved putting trash onto land.

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• Sanitary landfills are lined at base with layers of clay & plastic.

• Beneath this are areas designed to collect leachate – which is contaminated water formed as rain water flows through waste & picks up dissolved chemicals.

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• Layers of waste are alternated with layers of clean soil & plastic liner.

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• Ventilation is important to allow explosive methane gas (product of decomposition) to escape rather than to build up.

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• In some landfills, methane is harvested & used as an alternate energy source.

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• Leachate is collected & treated so that it can be added back to waterways.

Incinerators: Burning of solid waste

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Advantages Disadvantages

• Don’t require much space
• No risk to groundwater
• Heat produced can be converted to energy (ex. Sweden)

• Even best incinerators generate air pollution
• Some small amount of waste still remains – although it is reduced by 90%
• More expensive than landfills

Recycling: process of reclaiming raw materials and re-using them

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Most focuses on 4 major categories:

1. Metal – prevents mining of nonrenewable resources
2. Glass – easiest to recycle, used over & over and cheaper than new glass
3. Paper – saves trees, lower quality after several uses
4. Plastic – made from leftovers in petroleum refining process

Is recycling even worth the effort??

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• Conserves resources
• Saves energy
• Not the complete solution

Best strategy is to REDUCE waste.

• Double-sided copies or shrunken copies
• Reduction in product packaging
• Material substitution – refillable bottles & cups

New problem of Electronic Waste.

• Estimated that only 18% of televisions & computer products are recycled. Most are sent to landfills.

• Make up roughly 2% of all waste

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Most e-waste is exported to developing countries where children comb through mounds of toxic electronics to scavenge for valuable parts.

What is meant by the term Municipal Solid Waste (MSW)?

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What are 3 ways to handle MSW?

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What is THE BEST way to deal with MSW?

Trash generated by homes, businesses & schools

1. Landfills (bury it)

2. Incinerators (burn it)

3. Recycle!!

REDUCE!!! (meaning use less & create less waste)

6 Jan 2026

Copy & complete:

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1. How is the growing human population lowering biodiversity?

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2. How is the growing human population affecting air quality?

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3. How is the growing human population affecting water resources?

7 Jan 2026

more housing removes natural habitats

more land to grow food removes natural habitats

greater demand for electricity

(globally still a lot of coal-fired)

more use of transportation (most use oil-source)

Loss in both quantity AND quality

• greater demand for drinking water
• greater demand for irrigation to grow more food
• greater demand for electricity (use water for steam)

What are the major 6

threats to biodiversity?

Climate Change

Overharvesting

BONUS

What are some of the major contaminants to our planet’s water systems?

Industry & Mining – runoff into the waterways

Construction – add sediments into our waterways

Heat – generated by factories & powerplants

Agricultural waste – from livestock & chemicals such as fertilizers and pesticides

BONUS

1. As human population approaches its carrying capacity, what factors could limit this fast growth?

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2. What practices could be put in place today, that could increase the carrying capacity of humans on Earth?

8 Jan 2026