Environmental Science: A Comprehensive Guide to Ecosystem Sustainability
1. Environmental Science and Ecosystems
The natural world is organized into interconnected units called ecosystems. An ecosystem consists of a physical environment characterized by factors like temperature and moisture, the organisms that inhabit it, and the relationships between them.
Since the advent of humankind, human activities have allowed us to obtain food, housing, and transportation. This means we extract resources from ecosystems, impacting the environment. Humans are also subject to natural hazards.
The impact of humans on ecosystems is complex and requires an interdisciplinary approach. Environmental science draws on disciplines like chemistry, physics, law, economics, geology, biology, and ethics to identify, understand, and address environmental problems.
2. Overfishing: Limits of the Planet
A natural resource is anything humanity derives from nature to meet its needs. In terms of sustainability, natural resources are classified as:
- Non-renewable: Exhaustible resources like oil and minerals.
- Renewable: Resources that are not depleted if managed properly.
In 1600, the Earth’s population was 500 million. By 2050, it is projected to reach 9 billion. The demand for natural resources will be much higher. Population growth is not uniform across the planet, with half projected to live in India and China.
In many parts of the world, population growth exceeds the capacity of environmental resources to sustain it. This leads to environmental problems like overexploitation, pollution, and desertification.
3. Sustainable Development: The Way Forward
The problems arising from the overexploitation of natural resources are the result of an economic model based on consumption, waste, and pollution. The solution is sustainable development, which meets the needs of the present without compromising the ability of future generations to meet their own needs.
Sustainable development promotes a balance between the economic, social, and ecological dimensions of human development. This balance leads to a better quality of life, ensuring fairness between rich and poor while preserving the planet.
3.1. The Ecological Footprint
The ecological footprint, coined by William Rees and Mathis Wackernagel in 1996, measures the land area needed to produce the resources consumed by a citizen, town, or nation, as well as the area needed to absorb and detoxify the waste generated. Its main objective is to assess human impact on the planet.
The average ecological footprint is calculated by dividing the Earth’s productive land by the population. It is 1.7 hectares per person. However, annual consumption per capita is 2.8 hectares. Globally, we consume more resources than we produce and generate more waste than we can manage, making our current lifestyle unsustainable.
This leads to three consequences:
- It is necessary to reduce population growth.
- The lifestyle of the richest countries cannot be extended to all inhabitants.
- Consumption must be reduced.
4. Energy Resources
Population growth and economic development have led to increased energy consumption. Fossil fuels have been the most used but are considered non-renewable and produce pollutants. In recent decades, the use of renewable energy sources has increased.
4.1. Conventional Energy: The Usual Fuels
These include fossil fuels (coal, oil, natural gas), nuclear energy, and hydropower.
4.1.1. Fossil Fuels
Formed from the accumulation, burial, and transformation of organic matter, fossil fuels have high calorific value. They can be used directly in heating boilers (coal and natural gas) or after processing (petroleum). Oil is essential to modern society, providing gasoline, plastics, waxes, detergents, and textiles. However, it is a finite resource.
4.1.2. Nuclear Energy
Nuclear energy is obtained by converting mass into energy through fission (splitting large atoms) or fusion (combining small atoms). Currently, fission is used to generate electricity. However, nuclear waste remains radioactive for hundreds of years, posing a disposal challenge.
4.1.3. Hydropower
Hydroelectric plants use the energy of falling water to generate electricity. They require low maintenance and produce no pollutants. However, dam construction alters ecosystems, modifies river systems, and creates barriers for migratory fish. Smaller hydropower plants are being developed to minimize these impacts.
4.2. Renewable Energy Sources
Renewable energy sources have low environmental impact and are inexhaustible. The European Union aims for 12% of energy consumption to come from renewable sources by 2030.
4.2.1. Solar Energy
Solar energy, in the form of electromagnetic radiation (light and heat) from the sun, can be used directly or converted into other forms of energy. Solar thermal energy heats water, while solar photovoltaic energy generates electricity. The main drawback is dependence on weather conditions.
4.2.2. Wind Energy
Wind energy uses wind turbines to convert kinetic energy into electricity. Wind farms have a visual impact and can be inefficient in areas with low wind speeds.
4.2.3. Biomass Energy
Biomass energy is obtained from organic waste, mainly from plants. It can be used directly for combustion or to produce biofuels (ethanol, methanol, biodiesel). While it utilizes waste, it can produce pollutants like CO2 and has low efficiency.
4.2.4. Geothermal Energy
Geothermal energy utilizes hot water or steam from within the Earth. It is limited to volcanic areas.
4.2.5. Ocean Energy
Ocean energy harnesses the movement of seawater and temperature differences between water layers. It is still under development.
5. Natural Resources: Water
Water covers about 70% of the Earth’s surface and is essential for life. Most water is salty and unusable by humans. Only a small portion is freshwater, and even less is potable.
Water consumption per person has increased in the 20th century due to:
- Changes in diet, with increased meat consumption requiring more water than a vegetarian diet.
- Development of infrastructure like sanitation systems.
- Population migration to urban areas, where consumption is higher.
Access to water is uneven. Over 1 billion people lack access to potable water systems, and nearly half the world’s population lacks basic sanitation.
5.1. Water: A Vital Resource
Human history has been shaped by water availability. Most cities have developed near rivers. Water is essential for all biological reactions and processes.
The hydrologic cycle is the continuous process of water circulation between oceans, the atmosphere, and continents.
5.2. Water Uses
Consumptive use occurs when water is used for an activity and cannot be reused, such as in agriculture, industry, and urban settings.
Non-consumptive use allows water to be reused, such as in energy production and navigation.
Agriculture and livestock activities consume the most water (over 70%), mainly for irrigation. Industrial activities use water as a raw material, refrigerant, cleaning agent, etc., accounting for 22% of consumption. Urban use (8%) is related to living standards, population size, and economic development.
5.3. Water Overexploitation
Humans obtain water from rivers, streams, lakes, and groundwater. When water use exceeds the renewal rate, reserves decline. In many areas, especially groundwater reserves, this decline is alarming.
Overexploitation of groundwater occurs when extraction from aquifers exceeds the recharge rate. In coastal areas, this can lead to saltwater intrusion into aquifers.
Agricultural, livestock, industrial, and urban waste pollutes freshwater sources. Agricultural areas accumulate ammonia from septic tanks. Industrial waste can contain heavy metals and pesticides.
5.4. Water Management Plans
Hydrological planning regulates water use, addresses declining resources, and meets population demands within a sustainable framework.
Measures for optimal water planning include:
- Savings: Reducing consumption in various activities, including agriculture, industry, and urban settings.
- Technical measures: Building dams, reservoirs, water transfer systems, and desalination plants to increase water availability.
- Policy measures: Developing laws and agreements to address water scarcity.
6. Other Natural Resources
6.1. Soil: Life Support
Soil, a thin layer covering the Earth, is a mixture of minerals, organic matter, living organisms, air, and water that supports plant growth.
Soil formation begins with the colonization of bedrock by organisms with minimal nutritional needs, like lichens. Over time, lichen remains mix with eroded rock and are transformed by decomposers, creating nutrients for plants. Larger plants like mosses and ferns then colonize the developing soil layer, further weathering the rock and contributing to soil formation.
Soil provides plants with essential nutrients and water. A balanced soil contains approximately 45% minerals, 25% air, 25% water, and 5% organic matter.
Soil components are distributed in layers called horizons.
Soil is a non-renewable resource essential for ecosystem survival. Threats to soil include erosion, organic matter decline, contamination, salinization, compaction, biodiversity loss, landslides, and floods.
6.2. Soil Uses
Agriculture and livestock are the main drivers of land-use change. Urban expansion also transforms the ground, leading to habitat reduction, landscape fragmentation, and reduced space for species.
Economic growth has often come at the expense of soil destruction. Agricultural areas (crops and pasture) occupy about 11% of the Earth’s surface. In Spain, this figure is 50%, mainly for rainfed crops.
7. International Commitments
For decades, humanity has faced an environmental crisis and has attempted to address it through summits and international treaties. Some milestones include:
- Stockholm Conference (1972): Participants agreed on an ecological worldview and recognized human influence on the environment.
- Tbilisi Conference on Environmental Education (1980): Environmental education was recognized as a key tool to combat environmental degradation.
- Brundtland Report (1987): Critiqued the development model of industrialized countries and defined sustainable development.
- Rio Earth Summit (1992): Adopted commitments on climate change and biodiversity, and produced Agenda 21, outlining strategies for sustainable development.
- United Nations Framework Convention on Climate Change: New York (1992), Kyoto Protocol (1997), Buenos Aires Conference (1998), Hague Summit (2000), Johannesburg Summit on Sustainable Development (2002), Bali Summit on Climate Change (2007).
Citizens have a responsibility to think globally and act locally, adopting measures that contribute to sustainable development, such as saving water and energy and participating in waste recycling.