Man and Environment: Population Growth, Ecosystem Services, and Deforestation

Institution: Alexandria University, Faculty of Science.
Course Title: Man and Environment.
Lecturers: Dr. Khaled Mahmoud and Dr. Mohamed Zakareya.
Lecture Topic: Environmental Problems, Population Growth, and Deforestation.
Lecture Number: Lecture $5$ .
Date: March $24$ , $2026$ .

Overview of Major Issues: The lecture identifies four primary reasons for the manifestation of environmental problems: * Overpopulation: The exponential growth of the human species. * Deforestation: The large-scale removal of forest cover. * Pollution: Classified into three specific categories: * Air pollution. * Water pollution. * Land pollution. * Climate Change: The long-term alteration of temperature and typical weather patterns.

Historical Trends: World population growth was initially a slow process, but it experienced a "tremendous change" following the Industrial Revolution.
Milestones in Population Growth: * Year $1800$ : The world population reached its first $1,000,000,000$ (one billion). * Year $1930$ : The second billion was reached. This growth took approximately $130$ years from the first billion. * Year $1960$ : The third billion was reached, occurring in only $30$ years. * Year $1974$ : The fourth billion was reached, occurring in only $15$ years. * Year $1987$ : The fifth billion was reached in only $13$ years. * $20^{th}$ Century Growth: Over the course of the century, the population expanded from $1.65$ billion to $6$ billion. * Year $2024$ : The global population is approximately $8$ billion.

Definition of Population Growth Rate: This is the rate at which the absolute number of individuals within a population increases over a specific time period.
Mathematical Expression: The growth rate is expressed as a percentage ( $\%$ ) of the total number of individuals existing in the population at the start of the measured period.
United Nations (UN) Projections: * By mid- $2030$ , the population is projected to reach $8.6$ billion. * By mid- $2050$ , the population is projected to reach $9.8$ billion.
Current Metrics and Trends: * The current annual increase is estimated to be approximately $70$ million people per year. * Peak Growth: The annual growth rate reached its maximum point in the late $1960s$ , when it was approximately $2\%$ . * Current Decline: Since that peak, the rate of increase has nearly halved. It is expected to continue declining in the future. * Relative Growth: While the world population will continue to grow throughout the $21^{st}$ century, it will do so at a significantly slower rate than in the recent past. * Historical Doubling: The world population achieved a $100\%$ increase in the $40$ years between $1959$ (at $3$ billion) and $1999$ (at $6$ billion).

Extraction of Natural Resources: Population growth necessitates the increased removal of materials from the environment, including: * Fossil Fuels: Oil, gas, and coal. * Minerals. * Trees. * Water. * Wildlife: With a specific emphasis on marine life in the oceans.
Freshwater Consumption: Increased demand for water is driven by: * Drinking requirements. * Agricultural needs. * Industrial processes.
Ecological and Habitat Impacts: * Construction of Urban Areas: Includes the development of buildings and roads to accommodate more people. * Habitat Disturbance: Forests and other natural habitats are destroyed or disturbed during urban expansion. * Biodiversity Loss: These disturbances lead to a marked decrease in global biodiversity.
Land Use for Agriculture: As populations expand, more land must be converted for agricultural activities to grow crops and maintain livestock.
Species Exploitation: Increased rates of fishing and hunting lead to a reduction in the populations of exploited species.

Disease Transmission: High population density leads to the increased transmission of infectious diseases.
Sanitation and Water Access: * Overpopulation leads to limited access to adequate sanitation facilities. * Lack of clean drinking water is a major concern. * Over $2.6$ billion people currently lack decent bathroom facilities, forcing them to use rivers and backyards for waste disposal.
Respiratory Diseases: Growth in vulnerable populations increases severe respiratory issues caused by: * Breathing smoke from open fires. * Using poorly vented stoves for cooking and heating inside homes.

Corporate Externalities: Companies use environmental resources to produce goods for consumers but often do not pay for the harmful environmental costs associated with supplying those goods.
Timber Example: A timber company pays the direct costs associated with clear-cutting a forest but does not pay for the resulting environmental degradation or the loss of wildlife habitat.
Natural Capital: Actual market prices do not reflect the true value of "Natural Capital" ( لا آشمل قفمة رأس المال الطبفعى الأءففى}$$).
Valuation Definition: This economic process involves measuring the specific benefits and services that ecosystems provide to humanity.

Definition: The permanent removal of trees from a forested area.
Ecological Disruption: Deforestation breaks the ecological balance maintained by nature.
Anthropogenic Causes: Human activities driving deforestation include: * Agriculture (clearing land for crops). * Grazing (livestock maintenance). * Fuel (using timber as a source of energy). * Construction. * Manufacturing.
Consequences of Deforestation: * Increased Soil Erosion: The removal of roots and canopy leaves soil vulnerable to wind and water. * Loss of Soil Fertility: Because trees are removed, plant decay (organic matter) cannot return nutrients to the soil. * Hydrological Disruptions: Increased frequency and severity of both floods and droughts.