Ecological engineering combines the study of ecosystems with engineering methods to plan, create, build, fix, and take care of environments that connect human communities with nature. This helps both people and the natural world to thrive together.

Origins, key concepts, definitions, and applications

Ecological engineering became a new idea in the 1960s. It took many years to clearly define it. Its use is still being improved, and it has only recently been widely recognized as a new way of thinking. Howard Odum and others introduced ecological engineering as a method that uses natural energy sources to manage and control environmental systems. The idea began with Odum’s work on ecological modeling and simulating ecosystems to understand how energy and materials move through them.

Mitsch and Jorgensen identified five main ideas that set ecological engineering apart from other methods: 1) it uses the natural ability of ecosystems to design themselves; 2) it tests ecological theories in real-world settings; 3) it uses systems-based approaches; 4) it helps save non-renewable energy; and 5) it protects ecosystems and their living parts.

Mitsch and Jorgensen were the first to describe ecological engineering as designing services that help both society and nature. They later added that these designs should be based on systems, be sustainable, and connect society with its natural environment.

Bergen and others defined ecological engineering as: 1) using ecological science and theory; 2) applying it to all types of ecosystems; 3) using engineering design methods; and 4) following a set of guiding values.

Barrett (1999) gave a more direct definition: "designing, building, operating, and managing landscapes or water systems and the plants and animals in them to help people and, often, nature." Barrett also said other similar terms include ecotechnology and terms used in erosion control, such as soil bioengineering and biotechnical engineering. However, ecological engineering should not be confused with "biotechnology," which refers to genetic changes at the cellular level, or "bioengineering," which involves creating artificial body parts.

Ecological engineering applications are grouped into three sizes: 1) small areas (about 0.1 to hundreds of meters); 2) ecosystems (one to tens of kilometers); and 3) large regions (more than tens of kilometers). The complexity of the designs likely increases with the size of the area. As more opportunities to use ecosystems as links between society and nature are explored, the field’s definition may change.

Ecological engineering has focused on creating or restoring ecosystems, such as repairing wetlands or building systems that use microbes, fish, and plants to treat human wastewater and produce useful products like fertilizer, flowers, and clean water. In cities, ecological engineering has worked with fields like landscape architecture, urban planning, and urban gardening to improve human health and biodiversity, as aimed by the UN Sustainable Development Goals, through projects like managing stormwater. In rural areas, it has included restoring wetlands and reforesting communities using traditional knowledge. Permaculture is an example of a separate field that developed from ecological engineering, influenced by Howard Odum’s work.

Design guidelines, functional classes, and design principles

Ecological engineering design combines systems ecology with engineering design. Engineering design usually includes steps such as identifying a problem (goal), analyzing the problem (constraints), exploring possible solutions, choosing the best solution, and creating a complete plan. Matlock and others created a design framework that considers ecological time when evaluating solutions. When choosing between options, the design should use ecological economics and follow a value system that supports protecting nature and benefits society.

Ecological engineering uses systems ecology and engineering to understand how society and nature interact. One example is using Energy Systems Language (also called energy circuit language or energese) by Howard Odum to simulate ecosystems. This method helps define the system being studied, set its boundaries, and show how energy and materials move into, through, and out of the system. This helps identify ways to use renewable resources through natural processes and improve sustainability. A system is a group of parts connected by interactions that work together to achieve a purpose. Understanding systems ecology helps ecological engineers design projects that use natural components and processes, use renewable energy, and improve sustainability.

Mitsch and Jorgensen identified five Functional Classes for ecological engineering designs:

• Ecosystems used to reduce or solve pollution. Examples include using plants to clean polluted water, creating wetlands to treat wastewater, and using rain gardens to filter stormwater.
• Ecosystems copied to solve resource problems. Examples include restoring forests, creating wetlands to replace lost ones, and planting rain gardens to increase tree cover in cities.
• Ecosystems restored after damage. Examples include fixing polluted land, restoring lakes, and rebuilding river habitats with healthy plant areas.
• Ecosystems changed in a way that protects the environment. Examples include carefully cutting trees, managing fish populations, and adding predator fish to reduce algae growth.
• Ecosystems used without harming balance. Examples include farming that works with nature, raising multiple fish species in water, and planting trees on land to grow food at different levels.

Mitsch and Jorgensen also identified 19 Design Principles for ecological engineering. Not all principles apply to every project:

• Ecosystem structure and function depend on the forces acting on the system.
• Energy and resources in ecosystems are limited.
• Ecosystems are open systems that do not balance energy and matter perfectly.
• Focus on a few key factors is most helpful for solving pollution or restoring ecosystems.
• Ecosystems can adjust to changes and reduce their impact.
• Match recycling processes to the speed of ecosystems to reduce pollution.
• Design systems that handle changes over time.
• Ecosystems can design themselves naturally.
• Ecosystem processes occur over specific time and space scales that should be considered.
• Protecting biodiversity helps ecosystems maintain their natural balance.
• Transition areas between ecosystems are as important as cell membranes.
• Connect ecosystems where possible to improve function.
• Ecosystem parts are linked in a network; consider both direct and indirect effects.
• Ecosystems have a history that shapes their development.
• Ecosystems and species are most at risk near their edges.
• Ecosystems are part of larger landscapes.
• Physical and biological processes interact; both should be studied.
• Eco-technology should consider all parts of a system together.
• Information in ecosystems is stored in structures.

Before starting an ecological engineering project, Mitsch and Jorgensen recommend:
– Creating a model to identify parts of nature involved in the project.
– Using a computer model to test the project’s effects and possible risks.
– Improving the project to reduce risks and increase positive outcomes.

Relationship to other engineering disciplines

The field of Ecological Engineering is connected to the fields of environmental engineering and civil engineering. These three areas often share similar work in water resources engineering, especially in managing and treating stormwater and wastewater. Although these engineering fields are similar, each has its own specific areas of focus.

Ecological engineering mainly works with the natural environment and natural systems, aiming to help people and the planet coexist more effectively. In contrast, civil engineering focuses on built structures and public projects, while environmental engineering centers on protecting public and environmental health by managing waste and pollution.

Academic curriculum (colleges)

In 2001, an academic curriculum for ecological engineering was suggested. Important parts of this curriculum include courses in environmental engineering, systems ecology, restoration ecology, ecological modeling, quantitative ecology, the economics of ecological engineering, and technical electives. These courses are supported by required courses in physical, biological, and chemical subjects, as well as integrated design experiences. According to Matlock et al., the design process should identify limitations, describe solutions over time in ecological systems, and include ecological economics when evaluating designs. The economics of ecological engineering has been shown through examples such as using energy principles for a wetland and using nutrient valuation for a dairy farm. Based on these principles, the first B.S. Ecological Engineering program was created in 2009 at Oregon State University.

In 2024, the US Accreditation Board for Engineering and Technology, Inc. (ABET) published new criteria for accrediting Ecological Engineering programs for the first time. To earn accreditation, B.S. Ecological Engineering programs must include:

• mathematics through differential equations, probability and statistics, calculus-based physics, and college-level chemistry;
• earth science, fluid mechanics, hydraulics, and hydrology;
• biological and advanced ecological sciences that focus on multi-organism self-sustaining systems at different scales, systems ecology, ecosystem services, and ecological modeling;
• material and energy balances; the movement of substances in and between air, water, and soil; and the thermodynamics of living systems; and
• applications of ecological principles to engineering design that consider climate, species diversity, self-organization, uncertainty, sustainability, resilience, interactions between ecological and social systems, and system-scale impacts and benefits.

Literature

• Howard T. Odum (1963), "Man and Ecosystem," Proceedings, Lockwood Conference on the Suburban Forest and Ecology, in: Bulletin Connecticut Agric. Station.
• W.J. Mitsch and S.E. Jørgensen (1989). Ecological Engineering: An Introduction to Ecotechnology. New York: John Wiley and Sons.
• W.J. Mitsch (1993), "Ecological engineering—'a cooperative role with the planetary life–support systems," Environmental Science & Technology 27:438-445.
• K. R. Barrett (1999). "Ecological engineering in water resources: The benefits of collaborating with nature," Water International 24: 182–188. doi: 10.1080/02508069908692160.
• P.C. Kangas (2004). Ecological Engineering: Principles and Practice. Boca Raton, Florida: Lewis Publishers, CRC Press. ISBN 978-1566705998.
• W.J. Mitsch and S.E. Jørgensen (2004). Ecological Engineering and Ecosystem Restoration. New York: John Wiley and Sons. ISBN 978-0471332640.
• H.D. van Bohemen (2004), Ecological Engineering and Civil Engineering works, Doctoral thesis TU Delft, The Netherlands.
• D. Masse; J.L. Chotte; E. Scopel (2015). "Ecological engineering for sustainable agriculture in arid and semiarid West African regions," Fiche thématique du CSFD (11): 2. Archived from the original on April 23, 2016. Retrieved March 23, 2019.