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The Human Population

• Humans' exploitation of global resources has a primary impact on all environmental systems.
• The global human population reached 1 billion in 1804.
• It took 123 years to double to 2 billion by 1927.
• Took thirty-two years to reach 3 billion and thirty-nine years to reach 6 billion.
• In November 2022, the population was at 8 billion.
• From 1974 to 2022,1 billion people were added every twelve years.
• Expect fourteen years to reach 9 billion, which may peak at over 10 billion by 2100.
• Density-independent and density-dependent factors control nonhuman population abundance and distribution, which also factor into human population growth.

Growth Rate

• Growth rate measures the percent change in a population over a year.
• In 1963, with 3.6 billion people, the human population grew 2.1% annually.
• Estimated growth rate for 2023 is between 0.83% and 0.9%.
• Growth rates are decreasing globally.
• The number of additional people each year is now about 70 million, less than the 76 million per year when the growth rate was 2.1%.
• Births, deaths, immigration, and emigration dictate a country or continent's growth rate.
• Growth rate equals all population additions minus all subtractions, divided by the total population:
• (births + immigration) – (deaths + emigration) / total population * 100 = %GR*
• To calculate percentage growth rate, multiply the result by 100.
• Migration and emigration are important for analyzing individual countries, up to one-third of population in the United States.
• For the entire world, the human birth rate is expressed as the number of births per 1,000 individuals per year: crude birth rate or CBR.
• The number of deaths per 1,000 individuals in the population per year is the crude death rate or CDR
• Excluding migration, the growth rate can be calculated: (CBR-CDR) /10 = %GR
• Adjust numbers to align with the percentage.
• Changes in growth rates can be determined by plotting birth and death rates over time for a country.
• If the birth rate is above the death rate, positive growth occurs.
• A small 1.3 billion people live in higher-income countries (Europe, North America).
• A huge 6.7 billion people live in lower-income countries which includes China and India.
• The population difference between developed and less-developed nations has not always been so significant.
• Sub-Saharan Africa continues rapid growth, at 1.5%, while higher-income countries have leveled off at 0.2%.

Population Size and Resource Use

• Each of the 8 billion people on Earth consumes, produces waste.
• Provisions of food and resources requires energy and mineral resources
• People generate demands for wood, plastic, steel, and energy
• Mining, processing, and disposal degrade and add to the pollution of the environment.
• The overall impact of human population is calculated:
• Environmental Impact = Population x Resource Use Per Person x Impact of Resource Used.*
• Comparing fossil fuel consumption to population shows environmental effects like air pollution, land degradation from extraction, and carbon dioxide.
• Factors for predicting future growth includes past trends.

Factors Affecting Population Growth

• Crude Birth Rate (CBR) = Total number of live births per 1,000 in the population annually.
• Crude Death Rate (CDR) = Total deaths per 1,000 in the population annually.
• Growth Rate (GR) = Percent population growth annually = ((Yr 2 - Yr 1)/ Yr 1) × 100 or (CBR-CDR)/10.
• Total Fertility Rate (TFR) = Average number of children born to her during a woman's child-bearing years.. Doubling Time (Tdouble) = Years for population to double at current growth rate.
• Infant Mortality (IM) = Number of infants per 1,000 live births who die before first birthday
• Life Expectancy (LM) = Average expected lifespan of an infant born in a year.
• %<15/>65 = Percent of population below and above age 65.

Fertility

• The human population includes 8 billion with births as inputs, deaths as outputs.
• Births rely on birth rate, deaths on death rate.
• The U.S. total fertility rate estimates 1.84 children per woman, or below two.
• Population growth and total fertility correlate; countries with higher growth have higher fertility rates.
• The replacement fertility rate is 2.1: 2.1 children on average are needed to replace parents.
• The U.S. is below replacement level, but immigration must be weighed also - projected almost one million per year.

Life Expectancy and Infant Mortality

• Life expectancy is the average years an infant can expect to live with current death rate.
• Reported for overall population and divided by sex, life expectancy is shorter for men due to workplace or lifestyle hazards.
• Gap has decreased as more women workers enter the workforce.
• Infant mortality = deaths of under one year children/1,000 live births.
• Life expectancy and infant mortality indicate the level of health care in a country.
• Crude death rate not a good public health indicator, rather, may be a population of older individuals needing to be weighed.
• Many developed countries have lower infant mortality rate than the U.S., although, spend less per capita.
• Universal health care, more generous pregnancy allowances, and disparity in black, Native American, and Hispanic health care contribute to the higher rate.
• A U.S. overall infant mortality rate is 5.4, 10.4 for Black people in the U.S. and 8.2 for Native Americans.
• Lower socioeconomic groups and those that live in poverty are also disproportionately exposed to pollutants that contribute to higher infant mortality.

Age Structure

• Assessing distribution is looking at percentage under age 15 and percentage over 65.
• Commonly reported %<15/%>65 value: gives the relative distribution: compares countries.
• For instance, Mexico =24/8 while the U.S. = 18/18.
• 24 percent of the population in Mexico is under age fifteen than in the U.S. (18%)
• Mexico had far fewer people over 65: 8 percent while the U.S. has 18 percent.
• Part of Nigeria which has the highest growth: 41 percent under fifteen years of age / only 3.3 percent is over 65.
• The measure doesn't show movement in and out of the <15 category.
• A diagram showing a range of ages produces an age-structure diagram.
• Indicates growth, fertility, life expectancy, or consumption patterns of a particular country.
• There are three broad groups or categories for these unique age-diagrams: widest at the bottom and smallest at the top, which means more younger people are present than older people.
• Pyramid Pattern shows population in developing countries: growth rates 2–3.5%. As long as the youngest age group is larger than the age group above it, the population continues to grow.
• More individuals are younger, more older and structure takes on like a column: still relatively slow growth-called a stable population.
• Other countries display negative growth: the rate must be below 2.1, each successively older, the group is always larger-tends to be an inverse pyramid-like structure-Italy, Japan, and Germany.

The Elements on Earth

• Earth formed roughly 4.6 billion years ago with the molten rock
• Heavy Elements sank towards the center
• Lighter elements upwards remained near the surface.
• Differentiation of material by density resulted in three distinct layers to our planet: Dense inner core, the mantle, and lighter crust
• the volume of Earth is made of eight % of the volume by Earths.
• Although the whole Earth is 35% iron, only six % is from the lithosphere.
• The soil that forms the Rocky shell area: approximately a 100 km thick lithosphere, where rocks are changed via the circle cycle.
• Weathering (physical or chemical breakdown degradation removes while erosion transports via water and wind.

The Lithosphere

• The atmosphere sources elements exist in gas form.
• Atmosphere
• Nitrogen (seventy-eight %)
• Oxygen (21 percent)
• Carbon dioxide- (0.036 percent)
• Carbon, hydrogen, and oxygen- because are most elements in life.
• Soil is an intermediate source of essential nutrients with only six nutrients in the soil, while sixteen are needed by plants.
• Plants take essentials up in ionic form and many as well in an aqueous phase.
• Exchange with soil to support roots.
• Hydrologic cycle instruments chemical transports as well
• Weather (physical /chemical reduction of breakdown degrees, elements while elements removed by hydrol-ocean/lands.
• The cycles of calcium, magnesium, potassium, and sulfur is used.

Cycles of Elements

• Are from rock and vegetation degrees also occur in limestone. magnesium.
• The "dust bowls" from drought and winds and poor agricultural practices all contributed dust.
• Calcium magnesium combine cannot leach as quickly, while potassium is the opposite
• Sulphur with dioxide of sulphur primarily taken up plants anthropogenic levels now greater and clean air efforts reduced sulfur in the U.S. in sulphate.
• Difference-sulphur from rocks in minerals including from volcanic emissions
• Various elements are involved.
• Connecting overlying biology to geology, and benefits.
  • Medium for plant growth.
  • Serve as primary filter water moves from atmosphere to wells etc.
  • Habitats wide bacteria/fungi/other animals: to biodiversity.
  • Organic matter: recyclers: take dead take plant and animal material and using into energy in process. -Organisms filter chemicals from waster systems-then return to atmosphere and groundwater soil.

Soil Horizons

• Although we aren't usually aware of it as we move over the ground beneath our feet, soils vary across a landscape, sometimes differing within only a few meters.
• Soil has three or more horizons, or layers categorized by the physical, chemical, and biological properties Soil in O layers/zones.
• Forest are the A mixed together, while mix can be from worms or humans.
• Soil for Topsoil, soil in O layers, and more. E horizon sometimes forms underneath the O layers, and is characterized by elements. Other Elements are normally leached like clay or iron and other. The horizons where the B are leached from the A occurs only in soils, All topsoils here are and B of it or C. Horizon, similar to rocks (parent which in) may include or plant. There are several forms, including State to, Climate time.

State Variables and Soil Formation

• Soils form two directions breakdown of rocks, minerals material is the decomposition of plants, animals contributing from the soil and type.
• So, organic are in soils to from (so organic).
• That greatly affects is by modified material climate with organisms five important causes variables progress such progress.

The Soils

• In the soil, Parent consists altered rock as they are underlying the surface of the soil.
• Rock material represents of or before.
• Material is what may have been and physical activity or for example sand.
• Soil leads to the plant life in area on top of surface in formation (the is weather).
• Of time the extremely important formation as more speed the processes. To, more breakage surfaces is also major: that are caused by how: that moves a soil warm; that tropical leech is the soil.
• And an effect has an formation with vegetation and vegetation as it and decomposes on that soil Topography
• The surface of the soil surface is the surface of its formation (the constantly) is subject formation and material erosion of soil.
• As landslides hazards can the subject to in areas there are slopes or at bottom surface of erosion surface and erosion occurs.
• Organisms and fungi make up 80 bacteria percent of soil breakdown by consuming organisms.
• Plants in soil enhance to several are day since release digestion. To improve is to increase help have PH.
• Time: and effect what have on for centuries: that soils to increase.
• And soils for and that with large rock on bare clock. Factors that cause a different and factors soils, or various size.

Soil and Degradation

• The degradation is agriculture, other and of plants.
• One with a water soils.
• Topsoil and to take season!
• Compost from of soil-more decades will in areas.
• Projected what to that nutrient: change at soils areas increase: that will, but the area is unknown.
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