Last updated September 8, 2025

What is Sustainable Development?

Definition and Conceptual Genesis of Sustainable Development

Sustainable development is a concept formalized in 1987 in the Brundtland Report by the World Commission on Environment and Development, titled "Our Common Future." It is defined as "development that meets the needs of the present without compromising the ability of future generations to meet their own needs." This approach is based on the interdependence of three fundamental pillars: environmental viability, social equity, and economic efficiency. The concept already emerged in the work of scientists like Rachel Carson (1907-1964), whose book "Silent Spring" (1962) warned about the environmental impacts of pesticides.

The Three Fundamental Pillars of Sustainable Development

These pillars are closely linked, and their imbalance compromises overall sustainability.

Environmental: protection of ecosystems and responsible management of natural resources.
Economic: ensuring viable and equitable growth.
Social: promoting equity, access to resources, and social justice.

Global and Scientific Challenges

According to Rachel Carson (1907-1964), environmental awareness is essential to reduce pollution and restore ecosystems. Furthermore, the work of James Lovelock (1919-2022) on the Gaia hypothesis highlights the interconnection of Earth's systems and the need to maintain planetary balance. Sustainable development thus addresses long-term challenges related to human survival and ecosystem stability.

Table of Key Sustainability Indicators

Sustainable development is not just a theoretical concept. It represents an essential scientific and operational framework to ensure the sustainability of human societies and environmental protection. The integration of the three pillars and the constant measurement of indicators help guide public policies and individual behaviors toward a viable future.

Key Sustainability Indicators
Indicator	Current Value	Sustainable Goal	Comment
CO2 emissions per capita	≈ 4.7 t/year	< 2 t/year	Measure of individual and collective climate impact
Deforestation rate	≈ 10 million ha/year	0 ha/year	Indicator of ecosystem and biodiversity loss
Access to drinking water	≈ 71% of the global population	100%	Measure of well-being and social equity
Waste recycling rate	≈ 20%	≥ 70%	Indicator of sustainable resource management
Biodiversity index	≈ -23% since 1970	Stability or increase	Assessment of species and habitat erosion
Renewable energy in the energy mix	≈ 15%	≥ 50%	Energy transition to limit emissions
Extreme poverty rate	≈ 9%	0%	Major social indicator for equity
Soil erosion	≈ 24 billion t/year	Maximum reduction	Direct impact on agriculture and food security
Air quality (PM2.5)	≈ 35 μg/m³ global average	< 10 μg/m³	Public and environmental health indicator
Primary education completion rate	≈ 90%	100%	Measure of access to education and equity
Ocean acidification	Average pH ≈ 8.1 (decrease ≈ 0.1 since 1750)	Limit pH decrease to ≤ 0.1 unit	Indicates increased acidity due to atmospheric CO2, impacting corals, shellfish, and plankton

pH Measures the Concentration of Hydrogen Ions H\(^+\)

pH is a measure of the acidity or basicity of a solution, defined by \(\text{pH} = -\log_{10}[H^+]\), where [H\(^+\)] is the concentration of hydrogen ions. A neutral solution has pH = 7, an acidic solution pH < 7, and a basic solution pH > 7.

Examples of Acidic, Neutral, and Basic Molecules

Hydrochloric acid (HCl) – pH ≈ 0–1
Sulfuric acid (H₂SO₄) – pH ≈ 1–2
Nitric acid (HNO₃) – pH ≈ 1–2
Acetic acid (CH₃COOH) – pH ≈ 2–3 in concentrated solution
Carbonic acid (H₂CO₃) – pH ≈ 3–4
Neutral water (H₂O) – pH = 7
Sodium bicarbonate (NaHCO₃) – pH ≈ 8–8.3
Calcium carbonate (CaCO₃) – pH ≈ 8.2
Ammonia (NH₃) – pH ≈ 11–12 in aqueous solution
Sodium hydroxide (NaOH) – pH ≈ 13–14
Potassium hydroxide (KOH) – pH ≈ 13–14