The most powerful terrestrial ecosystem on earth, the Grazing Lawn
When we consider pollinators as grazing animals, we need then to envision biotic communities with strong grazer affinities, and there is none more powerful than the grazing lawn. Tragically, current North American vegetation models used to inform restoration lack any equation concerning grazing, thus we are blind to the grazing lawn concept.
The foundational work by S.J. McNaughton in the Serengeti savanna advances the grazing lawn concept, and general principles are perfectly applicable to North American landscapes. Grazing lawns exist where herbivores concentrate in a specific space and time. Grazing lawns are a prominent component of savanna landscapes, where trees provide midsummer mast and shade that concentrate animals. The grazing animals tightly crop the midsummer vegetation creating “lawns” that are dominated by cool season lowing growing grasses and flowers. In North America, many of these species are members to the genera Anemone, Enemion, Thalictrum, Fragaria, Antennaria, Besseya, Hypoxis, Sisyrinchium, Geranium, Heuchera, Poa, Festuca, Agrositis, Gentiana, and Lobelia. The vegetation in the shade is different from the vegetation in full sun, and generations of open grown trees in the same space over time creates a different plant community in the partial shade than the adjacent plant communities in the total sun. This patchiness between shade and non shade areas, between tightly grazed and lightly grazed areas, maximized heterogeneity, biotic diversity, and pollinator habitat.
Many of these species were recently common in old North American pastures, providing excellent forage for mammals, birds, and pollinators. But in recent times, the cultural practice of pasturing groves has been replaced by confined animal feeding operations (CAFOs). The groves have over grown, and the ground layer has been replaced by bare soil and non-edible vegetation, a process termed “afforestation”. From a biosphere perspective, we see how highly evolved edible ecosystems have de-evolved into dysfunctional non-edible ecosystems; a threat to herbivores, humanity, and Gaia.
We can scale grazing lawns to exist in the shade under one savanna tree, in the shade of a savanna grove, or we can scale savanna as one large grazing lawn. Likewise, we can cast savanna as the dominant, most symbiotically advanced, and the most productive terrestrial ecosystem to ever exist. The affinity between grazing animals and edible savanna vegetation is not a casual relationship, but rather a highly evolved phenomenon.
Finally, there are many types of grazing lawns. Early explorers describe savanna as “park like”, or, and I get a kick out of the next two, as “artificial pastures or lawns”. These descriptions describe a vegetative memory of bison-elk lawns, similar to the Serengeti, where the large herbivores act as the big machines clearing any and all vegetation in their path, while smaller animals, scaling from deer, to rabbits, to mice, to invertebrates, act as the finishing carpenters, precision selection between blades, buds, and nectaries.
Grazing lawns can also be the product of smaller than bison and elk herbivores. Should we dare envision the impacts on vegetation by a pre Columbian beaver population estimated between 400 – 600 million organisms? Beaver lawns became landscapes following riverine corridors throughout much of the Northern Hemisphere. Beavers were a keystone species and ecological engineers for a variety of vegetations including; sedge meadow, wet prairie, aspen-parkland, beach, ash-swamp, alder, and pond communities. A multitude of animal species were likely dependent upon beaver lawns, from moose to bees and so many sizes in between. Likewise, I have observed muskrat lawns in prairies adjacent to marshes where the aquatic rodents annually graze the same patch, season upon season, maintaining pastures suitable to muskrat morphology, and dominated by low growth form vegetation, while the surrounding vegetation is dominated by tall wet mesic species. There’s even evidence on how rabbit lawns maintain low growth form flowering plant communities in the shade of cedar trees reducing the potential for catastrophic fire in chaparral savanna. I’m sure the list of animal lawns can be traced down to the smallest invertebrate herbivores, the point is, all scales need to be considered in order to restore anyone scale.
The grazing lawn biotic community represents the most evolutionarily advanced, productive, and provisional terrestrial ecosystem ever. A predictive framework based on the first and second laws of thermodynamics elucidates a biosphere trend towards maximizing solar energy capture and degradation through the grazing lawn model: a living earth desires to become, in multiple themes and variations, one large grazing lawn. The grazing lawn concept is first described by S. J. MacNaughton in a foundational paper titled “Grazing Lawns: Animals in Herds, Plant Form, and Coevolution”. Although the paper is based in the Serengeti, the general principles apply anywhere herbivores are/were common, including the Great Lakes Midwest Ecoregion. Prehistoric evidence suggests grazing lawns have been a prominent planetary feature for the past 30 million years, and are the emanation of many current plant and animal species including Poaceae, Asteraceae, Fabaceae, Bovidae, and Cervidae. Prior to Midwest settlement, grazing lawns were common throughout the region creating a mosaic of intensely grazed and lightly grazed patches across the landscape. Despite their prominence and functional capacity, grazing lawns are rarely described as target trajectories in restoration, mainly because North American vegetation models used to inform restoration are negligent to the symbiotic feedbacks between vegetation and herbivores. This presentation describes the grazing lawn concept and how it fits into the North American landscape, especially as a suitable substitute to urban lawns, including residential, commercial, and public spaces that still require some form of annual maintenance. Grazing lawn species, installation procedures and maintenance regimes are also described. Finally, we see how an urban grazing lawn model can be used to inform rural land restoration. Grazing lawns could again become a prominent landscape feature to the benefit of ecological integrity including wildlife, pollinators, water quality, carbon sequestration, food-fiber production and aesthetics.
In This Series
A Plan For A Better Future: Creating a Unified Pollinator Ecology
Premise 1: Pollinators are grazers
Narrative 2: The most powerful terrestrial ecosystem on earth, the Grazing Lawn
Premise 3: Cool season species are cool too
Premise 4: Decrease grass seeding rates, but increase graminoid diversity
Premise 5: Functional groups, niche theory, and seed mix design
Premise 6: Relax the current punitive genotype restrictions
Premise 7: High density patch planting
Premise 8: Nitrogen pollution is a serious threat to pollinators
Premise 9: Make hay, not war
Premise 9: More pollinator habitat through more frequent fire.
Premise 10: Afforestation, an unknown but significant threat to pollinator survival