Why We Need to Increase Plant/Insect Linkages in Designed

the key; every ecosystem service required by humans (and most other animals as well) is created either di- rectly or indirectly by plants. We have degraded ecosystem function by re- moving plants from local ecosystems, or by assuming that all plants function equally well in every environment. It follows that we can repair the damage Features we have inflicted on the typically built landscape simply by putting the right plants back. And who better to lead the way in this most noble endeavor than landscape architects and designers. Unfortunately, most professionals Creating Living Landscapes: Why We Need to in these two careers have not been trained in the fundamentals of ‘‘eco- Increase Plant/Insect Linkages in Designed logical landscaping.’’ Instead, programs in landscape architecture and design Landscapes have followed a centuries-old tradition of treating plants as tools of creativity: Douglas W. Tallamy1 decorations that can be combined with artistic hardscape to create beauty in our surrounds. Plants are indeed in- ADDITIONAL INDEX WORDS. host plant specialization, ecosystem services, herently beautiful but they are far biodiversity, landscape design, environmental landscape more than that; plants are essential SUMMARY. Specialized relationships between animals and plants are the norm in to sustaining life, both on earth and nature rather than the exception and landscape designs that destroy them also inourgardens.Weneedtoexpand degrade local ecosystem function. Plants that evolved in concert with local animals our expectations of what plants must provide for their needs better than plants that evolved elsewhere. The most common do in designed landscapes to include and arguably most important specialized relationships are those that have developed their critical ecological roles and between insect herbivores and their host plants. Here, I explain why this is so, why encourage new cross-discipline col- specialized food relationships determine the stability and complexity of the local food webs that support animal diversity, and why our yards and gardens are laborations among entomologists, essential parts of the ecosystems that sustain us. I also discuss how we can use our restoration ecologists, and the hor- residential and corporate landscapes to connect the isolated habitat fragments ticultural community to accomplish around us and produce valuable ecosystem services, and what we can do to make our this. This article will discuss features landscapes living ecosystems once again. common to all living landscapes and suggests simple strategies for incor- s the human footprint con- To believe there will always be suffi- porating them into our designed tinues to expand at the ex- cient oxygen, clean air and water, spaces. A pense of the natural capital carbon sequestration, pollinators, Nature equals specialized that sustains us, there is a growing and the biodiversity that produces need and increasing demand for these resources, regardless of how relationships residential, corporate, urban, and we treat local landscapes, or to sug- A pattern is emerging from con- suburban landscapes that generate gest that technology can effectively servation efforts around the world; if natural resources rather than de- replace them is folly in its most mis- you want to save a particular species, stroy them. At our current popula- guided form. you have to save the specialized re- tion levels, a culture that segregates Fortunately, we already have the lationships that support that species. humans from nature is not a sustain- knowledge required to integrate hu- If, for example, you want to save the able option and by whittling away at man habitats with the natural world. resplendent quetzal (Table 1), a gor- functional ecosystems, such a culture Indeed, the concept itself is ironic geous but endangered bird in Central has led to a reduction in the earth’s because humans are products of the America, you have to restore popula- ability to produce essential renewable natural world—one of millions of life tions of wild avocado trees because resources (also known as ecosystem forms that natural systems sustain the fruits of that species are an essen- services) by more than 60% (Millen- every day—and we have never been tial component of the resplendent nium Ecosystem Assessment, 2005). even partially independent of earth’s quetzal diet. If you want to save bounty. What types of landscapes are jaguars, you need to protect large Department of Entomology and Wildlife Ecology, capable of sustaining humans and populations of palm species that make University of Delaware, Newark, DE 19716. nature simultaneously? Ones that small palm nuts (as opposed to co- 1Corresponding author. E-mail: [email protected]. feature plants that interact with the conuts). Why these palms? Because doi: 10.21273/HORTTECH03699-17 species around them. Such plants are palm nuts are a critical and 446 • August 2017 27(4) Table 1. Taxonomic identification of organisms discussed in this article. tropics that they are the rule rather Common name Taxonomic nomenclature than the exception. What surprises many, however, Birds is that specialized relationships, par- Bluebirds Sialia species ticularly involving food webs, are Buntings Passerina species also the rule in the temperate zone, Carolina chickadee Poecile carolinensis and we cannot create living land- Crossbills Loxia species scapes if we exclude them. If you Doves Zenaida species want may apples to spread by seed, Finches Fringillidae you need a population of box tur- Flyctachers Tyranni tles. May apple seeds germinate best Great green macaw Ara ambiguus after passing through the gut of Gray catbird Dumetella carolinensis a box turtle that has eaten the may Hummingbirds Trochilidae apple fruit. If you want pileated Northern cardinal Cardinalis cardinalis woodpeckers in your neighborhood Orioles Icterus species you need trees that harbor large Red bellied woodpecker Melanerpes carolinus colonies of carpenter ants because Resplendent quetzal Pharomachrus mocinno carpenterantsarewhatthesebirds Tufted titmouse Baeolophus bicolor feed their young. If you want your Tree swallow Tachycineta bicolor wild blue phlox to produce viable Wood thrush Hylocichla mustelina seed, you need the plants that sup- Mammals port the larval development of Black bear Ursus americanus day-flying sphinx moths (native vi- Foxes Vulpes species burnums for the hummingbird Jaguar Panthera onca moth or native coral honeysuckle Peccaries Pecari species for the snowberry clearwing or virginia Raccoon Procyon lotor creeper for the nessus sphinx), for Reptiles thesemothsaretheprimarypollina- Eastern box turtle Terrapene carolina tors of phlox. Amphibians Even species that do not seem to Frogs Anura species depend on any specialized relationships Toads Anura species often do, especially during repro- Arthropods duction. Chickadees provide an ex- Spiders Araneae cellent example. As anyone with Insects a bird feeder knows, chickadees are Lepidoptera seed-eaters during the fall, winter, Hummingbird sphinx Hemaris thysbe and early spring. When the time Nessus sphinx Amphion floridensis comes to feed the young, however, Snowberry clearwing Hemaris diffinis chickadees join 96% of the terrestrial Coleoptera birds in North America and rear Ladybird beetles hymenoptera Coccinellidae their young on insects (data from Ants Formicidae Dickinson, 1999) and not just any Bees Apoidea insect; they feed nestling caterpillars, Digger wasps Crabronidae the larvae of moths, butterflies, and Hemiptera sawflies. Chickadee parents could Assassin bugs Reduviidae feed their young other abundant Damsel bugs Nabidae insects, but the overwhelming ma- Stinkbugs Pentatomidae jority of their prey during reproduc- Neuroptera tion is caterpillars. Those are not Lacewings Chrysopidae just any caterpillar, but those that Plants are not covered in hairs or spines. Black-eyed susan Rudbeckia hirta Because chickadees rear their young Mayapple Podophyllum peltatum on caterpillars, there will be no Palms Arecaceae chickadees where there are not Virginia creeper Parthenocissus quinquefolia enough caterpillars to bring a clutch Wild almond Dipteryx panamensis of eggs to independence from pa- Wild avacado Persea americana rental care. How many caterpillars are required to produce a clutch of chick- substantial part of the diet of pec- populations of wild almond trees adees? Carolina chickadees bring caries, the wild pigs that are jaguar because they are the only trees those somewhere between 390 and 570 prey. If you want great green macaws birds will nest in. Such specialized caterpillars to their nest each day, in the future, you need to restore relationships are so common in the depending on the number of chicks • August 2017 27(4) 447 FEATURES in the nest (Brewer, 1961). Parents live, work, farm, and play seems come by these adaptations through feed nestlings in the nest for 16– counter-productive at best. thousands of generations of exposure 18 d before the young fledge and How, then, can we design land- to the plant lineage in question, al- then for 30 d or more after fledging. scapes that support a diversity of in- though occasionally they coinciden- If we focus only on the caterpillars sect species that stay in a balanced tally possess enzymes that are able to required to reach fledging, it takes equilibrium with the natural enemies disarm an evolutionarily novel plant 6240–10,260 caterpillars to fledge that control them? Before we answer (Rosenthal and Berenbaum, 2012). a single clutch of chickadees,

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