Broadly speaking, biodiversity refers to all of the ‘kinds’ that can be observed in nature; kinds of species, kinds of ecosystems, kinds of populations and individuals. Biodiversity can be classified according to a spatial or biological hierarchy: at the largest scales, it includes variety in ecosystem types and ecosystem functions, habitat types and characteristics. At the organismal scale, it includes taxonomic diversity (for example, orders, families, genera, and species), diversity in species traits and ecological roles, and genetic diversity within species and populations. Biodiversity encompasses all types of variation observed in the natural world, including both living organisms and their habitats, as well as functions and phenomena like nitrogen cycling or seasonal mass migrations.

Ecosystem services refer to the crucial benefits that humans derive from the natural world. These include the provision of resources like food, building materials, and fuel, “regulating” services like the purification of water and moderation of flood flows, and cultural services encompassing all the ways that the natural world inspires people and guides societies. These services are irreplaceable, and in some cases, replicating them is economically or logistically impossible. The provision, quality, and reliability of these services is strongly affected by biodiversity; as we erode the variety of ecosystems, species, and genes in a system, these services become jeopardized. This means that biodiversity plays an essential role in maintaining and modulating essential services and resources without which human societies can’t persist.

Human modification of our environment is now so pervasive and far-reaching that we are recognized to be in a new geological era, the Anthropocene, in which our actions are the primary force influencing the planet. A key characteristic of the Anthropocene is a catastrophic mass-extinction, loss of biodiversity, and a disruption of natural processes. Species extinctions, environmental change from greenhouse gas emissions, and the loss of natural habitats have been accelerating for the last two centuries, and reached unprecedented rates in recent decades. The scientific consensus is that these losses, if not significantly slowed and reversed, will lead to irreversible reduction in ecosystem services and a rise in existential threats to people, including climate change and emerging infectious diseases like COVID-19.

Biodiversity isn’t restricted to faraway rainforests or remote wilderness areas. It exists in our own back yards, and urban biodiversity is often the most direct interface between societies and the natural world, where many ecosystem services are delivered. Biodiversity in human-dominated systems can be protected and enhanced with prudent management in ways that enhance ecological benefits to people.

The functions and services provided by intact and biodiverse ecosystems can synergize and contribute to infrastructure engineering goals in diverse ways. Better knowledge of biodiversity and nature can greatly enhance the outcomes of environmental decision-making for multiple stakeholders and increase project sustainability, legitimacy and trust.

Nature-based solutions are a key part of Engineering With Nature and involve the recognition and strategic use of ecosystem services to support engineering solutions to environmental and social challenges. Nature-based solutions are becoming a key strategy for achieving more sustainable, equitable and effective management for multi-national agreements, local and national governments, and non-governmental organizations alike. Nature-based approaches are especially well-developed and increasingly implemented in the field of water management, and have been used to combat flooding, increase aquifer recharge, protect marine and riparian shorelines, and purify polluted runoff. By incorporating and enhancing biodiversity, holistic approaches to infrastructure and water management can achieve mutual gains (or ‘win-win’) outcomes that benefit people, nature, and nature’s many benefits to people.