Night and Day: Is Restoration Ecology in the Dark?

For countless plants and animals, nighttime is the right time, as the song goes. Ecological processes during the night drive ecological functioning in so many ways. Mating (we include pollination in this bucket), hunting, nesting, and migration all require darkness for their proper expression for many species. In contrast, restoration ecologists are creatures of the day. We are primates and visual perception steers our actions and many of our emotions. Consequently, the goals of our projects often are based on the diurnal appearance and functioning of sites. Success is regularly measured by aesthetics and the joy of human visitors as they saunter through restored landscapes during the day. However, there is a critical role that nighttime ecological processes have for sustainable landscapes. If we are figuratively in the dark about nocturnal ecology, we may not reach our restoration goals.

For plant life, light is the source of both energy and information. Most photosynthesis occurs in daytime although some biochemical pathways need the night to complete the cycle, especially in hot and dry habitats (CAM cycle plants). However, there is also an information function of the dark upon which many plant species rely. Length of the dark period controls the flowering cycle for many species. Installation of night lighting in public parks, streetscapes, and institutional landscapes can interfere with the long night interval needed to elicit flowering. The communication between the plant and the lighting regime gets confused.

On one university campus, a wide biodiversity of plants was installed as a teaching aid in botany. But the nighttime lighting curtailed the initiation of flowering in many species and much of the planting palette became useless as a source of floral diversity. The campus planners were unschooled about the negative impact of artificial lighting. In this journal issue, the report of a coastal public park design mentions that the public insisted on nighttime lighting for safety. Of course, this is reasonable, public security is often the highest priority, but the goal of the project was to celebrate the natural world. The lighting interfered in many ways with ecological function. Fall coloration and timing of leaf drop also becomes modified by artificial lights and visitors to a restored habitat may receive a cheapened restoration experience for all the toil that the landscape designers contribute.

Additionally, pollination ecology requires many agents, and some animals are only active at night. Bats, hawk moths (Sphingidae), and some small mammals visit flowers only in the dark. Plant life has many adaptations to attract these animals, light color and strong odor, but this link in nature is invisible to daytime visitors to the habitats. Restoration designs should include nocturnal blooming plants to magnify the biodiversity total even though the mutualisms of the species are obscure to the general public.

For animals, the darkened arena of our projects is both a playground and the war zone. Most mammals are active in the night, different from human's daytime preference. In the dark they can feed, hunt unseen from their many enemies, and even have an easier time at thermoregulation in many habitats. The lack of color perception in many mammals can be explained by their low light activities. For bats, the evolution of echolocation frees them from the limits of darkness in finding their prey. For owls, the evolution of the face disk and extraordinary sound acuity gives them advantages in the dark over their defeated prey. Darkness in these ways has a creative force, not just a limit to mammalian activities.

For many insects, the night gives freedom from many voracious hunters. The chirps, buzzes, and clicks that fill our night air remind us that there is an unseen world around us that revels in the dark. Romance in the night is most obvious in habitats where fireflies magically glow. Evening falls, and they begin their illuminated courtship repertoire, thrilling visitors to restored landscapes. Darkness increases the chance that their brightly lit abdomens will be attractive to the hoped-for meeting with a partner. Light also interferes with the mating behavior of many other insect groups. All restored projects must balance the preference for light to...