Ecological Intensification & Perennial Polyculture
Naturally occurring plant communities, whether forests, prairies, deserts, savannahs, or tundra, are almost universally dominated by diverse perennial species.
Plant diversity is important because it helps to keep populations of plant-loving insects and diseases in check. Diversity also tends to enhance productivity because resources such as sunlight, water, and nutrients are used more efficiently when species with different resource requirements grow together.
With the intercrop systems, called polycultures, we hope to incorporate the benefits of diversity seen in nature.
Perenniality is important because when vegetation lives for many years, soils are not only protected against erosion, but they actually build and accumulate organic matter. Deep-rooted perennial plants are able to access nutrients and water that escape the reach of annual plants.
The Land Institute’s perennial breeding programs are working to replicate the perenniality that is commonplace in nature.
Ecological Intensification: The Big Picture for Perennial Agriculture
In contrast to naturally occurring plant communities, our current grain-producing plant communities – that is corn and wheat fields – feature annual crop species with typically low levels of diversity. It is entirely predictable, therefore, that our agricultural ecosystems tend to experience high levels of pest pressures, soil erosion, loss of soil organic matter, and nutrient leakage.
In recent years, researchers around the world have begun to propose that “ecological intensification” – that is, harnessing ecological processes to supplant the need for commercial inputs like fertilizers and pesticides – will be necessary to maintain food production while reducing environmental impacts of agriculture. By using models of naturally occurring plant communities, Land Institute researchers believe that previously unattainable levels of ecological intensification are possible with perennial polycultures.
Multiple Levels of Ecological Intensification
At The Land Institute, we’re working on three levels of ecological intensification to transform agriculture from having a degenerative to a regenerative impact:
All species in natural ecosystems have undergone many cycles of natural selection resulting in adaptations to specific ecological conditions. For example, many grass species have developed resistance to specific plant diseases. Genes coding for disease resistance can be incorporated into perennial crops through breeding. Perennialism is another trait that occurs at the species level and is controlled by numerous genes.
Plant communities in wild ecosystems usually feature many species. Biodiversity in plant communities helps to reduce disease and insect damage throughout the system, and helps plants take advantage of resources such as water, nutrients, and sunlight. Multi-species communities will help ensure more stable ecosystems for perennial grain agriculture.
It is extremely rare for wild ecosystems to remain in a disturbed state for very long. After disturbances like fire, drought, or floods, perennial species either re-sprout or germinate and take over dominance from ephemeral annual plants. Below ground, the quality of soil organic matter changes during succession as does the community of microorganisms that it supports.
What is Succession, and Why Does It Matter?
Ecological succession is a process of change that occurs after forests, grasslands, or other types of ecosystems have been disturbed by things like fire, floods, or drought. If disturbances are intense, ecosystems can be set back to very early stages of succession, often characterized by the proliferation of annual plant species, losses of nutrients, soil organic matter, and even topsoil itself.
In the wild, periods of high disturbance are almost always brief. No sooner does the ecosystem get knocked back with a disturbance such as a very hot fire, than perennial plants begin to sprout, soil organic matter begins to rebuild, soil microbes change, and the functioning of the ecosystem begins to improve.
In modern annual agriculture, we hold the ecosystem in the highly disturbed and highly compromised state indefinitely. By arresting succession, we make “permanent” a poorly functioning ecosystem that is extremely transient in natural ecosystems.
Perennial crops, which put far more energy into roots below ground and do not require frequent disturbance, allow for succession to take place once again. At The Land Institute, we are learning about the role succession plays in governing ecosystem functions in newly developed perennial polycultures.
Director of Research and Lead Scientist, Ecology Program
Lead Scientist, Crop Protection Ecology
Research Associate, Crop Protection Genetics
Eric A. Cassetta
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