0257-B1
Gregory A. Ruark[1]
Sustainable forestry and sustainable agriculture share many goals. Unfortunately, there is a tendency to treat agriculture and forestry separately when addressing natural resource concerns. Yet a high proportion of the watersheds and landscapes in this country are an interwoven mosaic of both uses. Together they comprise more than 75 % of the land use in the United States. Solutions are needed that build from a comprehensive, all-lands approach. Otherwise, it is like trying to make a patchwork quilt without bothering to sew the pieces together - everything comes unravelled. Agroforestry offers a set of conservation and production technologies that can help to integrate forestry and agriculture efforts. Some promising areas where agroforestry can assist agriculture and forestry to work in partnership to meet society’s goals are water quality, carbon cycles, silvopasture, biological diversity and green infrastructure in communities.
Over the past 50 years the earth’s population doubled to reach its current level of 6 billion. Today the world’s population is increasing by 80 million annually, with the total projected to reach 10 billion within 40 more years. Humanity must learn to live within the constraints imposed by the physical environment as both a provider of inputs and a sink for wastes. The fact that today more than 1 billion people do not have access to clean water and 1.7 billion lack basic sanitation illustrates that the demands of a growing human population and an expanding global economy are already placing considerable stress on natural systems. This raises huge challenges for policy-makers as they seek to reconcile the needs and aspirations of a growing population with resource limitations.
Globally, most of the arable agricultural land is already under cultivation. In the U.S. we still have some marginal farmlands on idle, for example under the Conservation Reserve Program, but a significant amount of prime farmland is now being lost to development pressures. For example, nearly 3 million acres of cropland, 6 million acres of pasture, and 10 million acres of rangeland were converted to commercial or residential use between 1982 and 1992. Similarly, forest cover in the U.S. has now started to decline after remaining essentially constant since the 1920’s. Forestry and agriculture will both be faced with the problem of meeting an increasing demand for goods, as well as for an expanding array of services, like clean water, recreation, and wildlife habitat. These needs will have to be met with a fixed or shrinking land base.
In the near future there will be many more people to feed, cloth, and house. Technology may provide some productivity gains as improved crops become available through biotechnology and genetic engineering, but the heavy reliance on fertilizers and pesticides is already manifesting its own not-too-subtle impact on the environment. Agriculture may be able to produce sufficient food and forestry sufficient wood but production costs will rise and so too will the cost of food and wood products, as well as the potential for negative impacts to the environment. We will also need to cope with the uncertainties of weather and climate change.
Ultimately the challenge will be to find ways to sustain the provision of goods and services that society derives from forests and agriculture in ways “
that meet the needs of the present without compromising the ability of future generations to meet their own needs.”
Agroforestry is the intentional blending of agricultural and forestry production and conservation practices. These technologies offer a suite of practices that can be readily integrated into the operations of many farms, as well as be modified to assist communities. In the temperate United States agroforestry involves the incorporation of trees and shrubs into existing farm operations rather than a land use change from agriculture to forestry. The benefits associated with the greater adoption of agroforestry technologies can help society achieve the goals of sustainable forest and sustainable agriculture.
Today many farmers and ranchers are struggling to make a livelihood on small acreage farms. They often have limited financial means and are seeking ways to maximize their income, while keeping their need for purchased inputs low. Although 60 percent of U.S. farms are smaller than 70 hectares, more than half of farm receipts are attributed to the six percent of farms with gross sales over $250,000. Over the past 20 years 300,000 small farms have been lost in the U.S.
Production systems need to become more diverse. New crops and new methods need to be embraced. A more diversified agricultural sector means that producers will need to select from a broad portfolio of management practices - practices that include science-based agroforestry technologies. In many instances, the cost-effective incorporation of one or several agroforestry practices can be the difference between profitability and economic loss.
When the USDA National Commission on Small Farms Report was issued in January 1998, it listed several recommendations on agroforestry and concluded “...USDA extension, conservation, and forestry services should make greater efforts to promote and support agroforestry as part of an economic and ecological strategy for a healthy agriculture.”
Although some agroforestry practices, like alley cropping, require a lengthy time period to establish and realize a return on investment or, like riparian forest buffers and windbreaks, are primarily designed to provide environmental benefits, there are several agroforestry practices that can be used to rapidly generate income. For example, existing farm woodlots can often be thinned to allow sufficient light to penetrate into the understory for the purpose of growing specialty or forage crops like ginseng, shiitake mushrooms, and decorative ferns that can be sold for medicinal, culinary, or ornamental uses. In addition, silvopasture systems, which incorporate managed forage and grazing under widely spaced conifers, have shown strong economic promise in the southeast.
The U.S. and Canada participated in the Montreal Process on sustainable forest management (SFM) and joined several other temperate forest countries in a commitment to SFM in signing the Santiago Declaration in 1995. Operationally, it seems less likely that a country will conclude that it is failing at SFM, but rather that in some regions, for some specific goods and services, it cannot meet society’s expectations. The first six of the seven criteria of the Montreal Process for SFM can be viewed as a statement of the goods and services that society derives from its forests:
1) Biological diversity
2) Wood and non-timber products
3) Healthy ecosystems
4) Soil and water resources
5) Carbon cycles
6) Multiple socioeconomic benefits
7) Legal and institutional framework
From this perspective, there are places in the United States that are already experiencing difficulty with some of these criteria. For example, in many areas the fragmentation of forests across the landscape has resulted in the reduction of many plant and animal species that rely on forest habitat. In other regions there are projections of inadequate wood supply. Insufficient water quality and aquatic habitat are issues that now affect most regions.
If we are to truly meet society’s needs and aspirations for forest-derived goods and services, we must find ways of augmenting traditional forestry by gleaning some portion of these benefits from agricultural lands. For example, windbreaks can provide corridors across agricultural lands to connect forest fragments, riparian forest buffers can protect surface waters from agricultural sediments, nutrients, and contaminants, hybrid poplars grown on farmlands can help meet the nation’s demand for wood fiber, and farm woodlots can be used to grow specialty products like ginseng or mushrooms under a modified forest canopy, thereby encouraging timber stand improvement practices.
Many aspects of society are challenged by the need to develop sustainably. The really difficult challenge will be to find solutions that strike a balance among the many sectors. Since population and consumption continue to escalate, sustainable development is really an optimization problem whose solution is changing over time as society strives to adapt to increasing pressures.
Agriculture and forestry share many of the same goals. Indeed, a high proportion of our watersheds are an interwoven mosaic of both uses. Agroforestry is a set of conservation and production technologies that brings these two sectors together. Some promising areas in which agriculture and forestry can work in partnership are:
Water Quality - Fresh water is one of our nation’s most important assets. Increasingly large supplies are needed for uses like irrigation of cropland, industrial and commercial applications, recreational activities, and drinking water for communities. In many instances the water must also be of high quality. Unfortunately, contaminants in many of our surface waters exceed national health and safety standards, with approximately 40 percent of our nation’s surface waters now not fit for fishing or swimming. This problem is now spilling over into our coastal marine ecosystems. Much of the water pollution can be attributed to two sectors:
Agriculture - About 70 percent of the non-point pollution of water in the U.S. comes from agricultural operations. Annually, in the United States 12 million tons of nitrogen (N) and 2 million tons of phosphorus (P) are added as commercial fertilizers, while an additional 7 million tons of N and 2 million tons of P are applied as manure. Each year, much of this fertilizer finds its ways into surface waters. The highest levels of N in streams are associated with agriculture and in areas where livestock are concentrated high phosphorus levels are also found. In addition, each year 1 billion pounds of pesticides are applied nationally, with about 75 percent of this application occurring in agriculture. Streams that course through agricultural fields are typically devoid of vegetation in their riparian zones. Runoff contains excess fertilizers, pesticides, animal wastes, and soil sediments and has led to the impairment of many of our freshwater resources. In fact, the level of N runoff from farmlands is so great that it now triggers a biological chain reaction each summer in the Gulf of Mexico that depletes the oxygen from an area covering 8,000 square miles. Commercial fishermen call this hypoxia zone the “dead zone”.
Agroforestry technologies, like riparian forest buffers, have been shown to be effective in using trees to reduce water pollution from agricultural activities. These buffers can slow and reduce the transport of runoff to streams, thereby allowing more time for the environment to degrade pesticides and animal waste products and increasing the infiltration of water and contaminants into the soil.
Community Stormwater Runoff - As a community grows, land that was once covered with vegetation becomes surfaced with houses, businesses, and pavement. Storm drains and impervious surfaces replace the natural functions of the landscape that absorb, filter, and transport rainwater. Rain concentrates in gutters, driveways, parking lots, and streets and is collected by stormdrains. Immense volumes of this stormwater reach surface waters at high velocities and containing numerous contaminants. The Clean Water Act now requires communities to develop plans and treat stormwater to improve its quality. A set of concrete pipes that simply passes stormwater onto downstream neighbors is no longer acceptable.
Agroforestry approaches that utilize trees, shrubs, and grasses to manage stormwater runoff are being adapted to meet community needs to detain and treat stormwater. The vegetation can also act as a living filter to improve water quality downstream and protect stream channels.
Carbon - Agricultural activities occur on almost half of the land in the contiguous U.S. and much of the opportunity to store carbon through afforestation will occur on farms and ranches. Agroforestry can play a significant role in the carbon balance cycle when proper attention is given to site location, species selection, and management. Windbreaks not only increase carbon storage in the vegetation and roots, but also provide energy conservation by reducing heat loss in farmsteads, feed costs to livestock, and snow removal costs. Field windbreaks reduce irrigation water loss, keep nutrient rich topsoil in place and improve crop production. Riparian buffers are natural carbon sinks. When suitable trees and shrubs are grown in these moist environments they also filter out excess nutrients coming from adjacent agricultural or urban activities. Short rotation woody crops, like hybrid poplars, can sequester and store carbon rapidly while treating agricultural, livestock, and community wastes. All of these agroforestry practices improve soil carbon storage by reducing annual tillage and can provide additional carbon storage in wood products derived from the trees.
Silvopasture - Research has demonstrated that many forage plants will yield high levels of quality biomass when grown under up to fifty percent shade. This knowledge is being used to design agroforestry timber/grazing systems in pine stands. These “silvopasture” systems allow trees to be grown as a long-term product, while on the same piece of ground an annual income can be generated from grazing livestock. In a silvopasture system trees are grown at a low stocking density to allow about half the sunlight to reach the ground to grow forage. Forest management is encouraged as trees must be thinned and pruned periodically throughout the rotation to maintain the proper light level for forage. As a result, most of the wood produced is sawtimber or veneer quality, which can be sold for several times the price of pulpwood. While landowners see economic diversification as the main reason for establishing this new practice, other benefits include erosion control, improved wildlife habitat, and carbon sequestering. In addition, the low tree stocking rates and managed understory of silvopasture systems makes them inherently low risks for damage by catastrophic wildfires.
Biological diversity - There simply is not enough forested habitat in some landscapes to support many species of plants and animals. Agroforestry provides ways of augmenting the supply of forest habitat. If spatial arrangement is considered agroforestry plantings can also be used to connect forest fragments and other critical habitats in the landscape. Where croplands occupy most of the landscape, linear riparian zones and field windbreaks have been argued to be essential in maintaining plant and animal biodiversity, especially under a changing climate scenario. Agroforestry adds plant and animal biodiversity to landscapes that might otherwise contain nothing but monocultures of row crops. Windbreak plantings can be designed to optimize wildlife benefits by using designs that are wider and incorporate several native species of trees, shrubs, grasses, and other plants. Riparian forest buffers that are now primarily designed to protect streams and surface water quality can be modified to increase their benefit for conserving plant and animal biodiversity.
Green Infrastructure in Communities - People who live in urban/suburban areas have become increasingly concerned with the accelerating loss of open and green space. This is a quality-of-life issue to many and raises the potential for agroforestry applications at the agricultural/community interface to restore ecological functions that provide for stormwater management, wildlife habitat, recreational opportunities, and aesthetic enhancements. Communities have long understood the need for “gray infrastructure” like water and sewer lines, power lines, and roadways. More recently, the importance of “green infrastructure” that consists of a planned and managed, interconnected network of natural areas (waterways, wetlands, forests and conservation lands like greenways and parks) and adjacent working lands (farms, ranches, and corporate lands) has gained recognition in many communities. Together these lands have the potential to support wildlife, maintain ecological processes, sustain air and water resources, and contribute to the health and quality of life for communities. Green infrastructure, as an integral part of the urban and rural landscape, can provide the strategic conservation framework needed for environmental, social, and economic sustainability.
Summary - Agroforestry is relevant to many issues that society cares about and it can help achieve many of the goals of sustainable forestry and sustainable agriculture. Unfortunately many resource professionals and landowners don’t see the connections. Agroforestry technologies need to become an integral part of a natural resource professional’s toolbox. Otherwise, as the old saying goes, “If the only tool in your toolbox is a hammer, everything begins to look like a nail.” With more than 80 percent of U.S citizens now living in urban or suburban environments it has become increasingly important that people understand that much of what they value is derived from agriculture and forestry. They need to understand that clean water does not just happen; that the food and fiber they consume and the wastes they generate have associated consequences and responsibilities.
| [1] Director U.S.D.A. National
Agroforestry Center, East Campus - UNL Lincoln, Nebraska 68583-0822. Tel:
(402) 437-5178; Email: [email protected];
Website: www.unl.edu/nac |