A truly natural pond is one that has formed without the influence of human activities. Natural ponds may be small or large, ephemeral or ancient, and they may or may not support a full spectrum of wildlife. Natural ponds can age and die, and they may not always be healthy, but they’re part of an ecosystem, nonetheless.
In contrast, manmade ponds are also part of an ecosystem, no matter what style or purpose they were constructed for, but they may not intentionally support any type of wildlife, whether by circumstance or design. Manmade “natural” ponds are, therefore, strictly speaking, simply a style of constructed pond, specifically designed to look and feel like the kind of natural pond one might find in an undisturbed setting. Nonetheless, these “natural” style ponds may even discourage biodiversity, depending on how they’re designed and managed.
In contrast, wildlife and ecosystem ponds intentionally provide habitats for a variety of creatures and, by doing so, actively promote biodiversity. Even so, there are some key differences between the two.
Wildlife Ponds
Wildlife ponds are designed to attract a wide variety of native wildlife and provide food and appropriate habitats. The wonderful thing about these ponds is that it actually takes concerted effort to prevent wildlife from showing up. Simply turn your back on a well-established pond for a few minutes and you’ll find evidence of visiting birds, bugs, frogs, turtles, and mammals! Even better, wildlife ponds can be integrated into all types of gardens: large or small, formal or free form.
Whether a wildlife pond is an integral part of a larger wildlife garden, or a hidden gem in a strictly formal space, it can be as simple as a small depression filled with water, or as intricate as a spreading, multilayered pond with multiple depth changes. It may include a variety of plants to provide food, cover, and maintain water quality, a few logs for cover or basking, as well as natural substrates to support vital invertebrate and microbial populations. These ponds generally focus on biodiversity and play an important role in preserving many species who are under pressure from habitat loss and other disruptions caused by human activity. While wildlife ponds may have an informal character and superficially resemble ecosystem ponds, they’re often focused on terrestrial wildlife populations rather than aquatic systems. These ponds need regular support and maintenance to maintain high quality water capable of supporting frogs and newts, as well as drinking water for other wildlife visitors.
Depending on an owner’s preferences, ponds intended to support wildlife will often include fish, but it’s important to realize that they are easier to maintain without the additional biological load of koi or goldfish. Without them, a pond’s nutrient load and water chemistry is typically more stable, and it often won’t need water filters, pumps, or regular water testing and chemical treatments.
Ecosystem Ponds
Ecosystem ponds, in contrast to wildlife ponds, focus on establishing a full, balanced aquatic ecosystem that closely replicates a complex, self-sustaining cycle of birth, death, and renewal. One area where man-made ponds, including ecosystem ponds, simply cannot replicate their natural inspiration is the issue of water exchange. Healthy ponds, in nature, are attached to rivers or springs, which provide a constant inflow of fresh water and allow the same amount of “dirty” water to escape. This is essentially nature’s version of a water change.
Water changes are necessary to maintain any man-made aquatic habitat. When old water is removed, it removes excess nutrients and harmful decomposition byproducts like nitrates and helps maintain proper pH. Fresh incoming water brings in oxygen, replenishes important nutrients, and promotes circulation and mixing with the old water.
In a man-made pond, however, no matter how “natural” you try to make it, water changes need human help, and the more waste-producing aquatic organisms like fish and turtles that live there, the more frequent the water changes will need to be. In truly natural situations, a pond that has lost its connection with a river, stream, or spring has taken its first steps toward eutrophication, or the process of aging and eventual death of a pond or lake. Without specific support measures, your ecosystem pond is no different.
To correct for the lack of a natural mechanism for water exchange, a well-designed ecosystem pond should include a biological filter to convert harmful waste by-products like ammonia to less harmful nitrites and, again, to nitrates. While nitrates, in high concentrations, are still harmful to fish, marginal and aquatic plants are happy to take them up as nutrients.
To ensure this “cycle of life” in an ecosystem pond is functioning, a pump should also be used to ensure water is in motion throughout the pond, leaving no stagnant areas or oxygen-free zones. In nature, ponds accomplish this through their connection with moving surface water or springs. Delicately balanced systems like eco-ponds won’t function well without that support.
There are many other “moving parts” in an ecosystem pond, and probably no other part is as critical as the plants you introduce into and around your pond. Check out more information in our next article in this series, “The Power of Plants.”
Because an ecosystem pond is intended to replicate a complex cycle of birth-death-renewal for an interdependent set of organisms, it will often require significantly more effort and attention in the beginning stages, before the ecosystem has achieved a state of (supported) equilibrium. Regular water testing, seasonal removal of debris like leaves and algae, monitoring the health of plants and aquatic residents like fish, frogs and turtles, and regular pump and filter maintenance are small efforts to make towards a slice of paradise, buzzing with bees and dragonflies, splashing with frogs and fish, and sunning with turtles and lizards.
