A key finding is that overnight charging currently has the lowest absolute level of CO2 emissions and a relatively low variance compared to other times of charging. This may not imply that an EV solution is categorically preferred on the grounds of net CO2 emissions compared to a baseline HEV, although the research does permit such quantitative comparisons. And it does convey actionable information given the vast temporal optionality currently allowed for charging. Going forward, we can envision a means of aggregating the impacts of individual analyses, meaning that these events will be weighted based on their likelihood and current behaviors. We can furthermore consider behaviors will evolve as time goes by and as larger shares of EVs are realized. However, within a transition period where EV growth and grid dynamics adapt iteratively, this study conducted novel simulations of the primary grid-vehicle scenarios which are reflective of current EV behavior and grid characteristics in recent years. The study’s consultations with experts, literature review, and data analysis revealed that about ¾ of events occur at home, with 50% on a level two charger and 25% on a level one charger. This would suggest, for the near and intermediate term, that EVs will act as a kind of aggregated demand in the evening/overnight hours and that as a block , EVs are more likely to require marginal resources because they act together to force demand projections out of the expected regime. The good news is that, for the foreseeable future, these are, on balance, curing cannabis hours that are moderately lower in terms of marginal resource carbon intensity, since they can be met by intermediate resources . Whereas workplace charging is substantially less common, perhaps the marginal mix or the hourly estimation is reasonable for the effective CO2 signatures.
As one thinks about the scale, and a situation where of EV reach double-digit shares of the fleet, it’s very likely that all the modes and locations of charging will eventually be subject to conditions where marginal assumptions prevail. How the transition period is defined and how the system boundaries between EV growth and grid resources are balanced are important, but open questions. Another essential unknown that will impact effective CO2 emissions from EVs are how predictable EV charging events become, with an emphasis on the high power, coincident peak events. More research into this question can help inform more accurate methods and models for simulating the environmental impacts of EVs. The present framework sets up an approach that will be valuable in estimating future impacts under such conditions. While additional focus and scope lie beyond this study, it is clear that a more complete understanding of popular EV charging profiles and EV driving behaviors will be essential inputs to better decision-making and resource planning. As EV use and charging habits become more predictable and well-known, the relevant data and insights can be critically valuable to utilities. For instance, foreknowledge of EV charging events will be needed at an aggregate level and could be beneficial to grid operators. The reason is that they can better plan and iterate their learning for those types of loads and events for which currently they lack visibility.In the last 40 years, 30 percent of the world’s arable land has become unproductive and 10 million hectares are lost each year due to erosion.1 Additionally, accelerated erosion diminishes soil quality, thereby reducing the productivity of natural, agricultural and forest ecosystems. Given that it takes about 500 years to form an inch of topsoil, this alarming rate of erosion in modern times is cause for concern for the future of agriculture.
This supplement explores the major causes of soil erosion and the social impacts it has on communities, underscoring the importance of agricultural practices that prevent or minimize erosion. Anthropogenic causes of accelerated soil erosion are numerous and vary globally. Industrial agriculture, along with overgrazing, has been the most significant contributor, with deforestation and urban development not far behind.2, 3, 4 Heavy tillage, fallow rotations, monocultures, and marginal-land production are all hallmarks of conventional agriculture as it is variably practiced around the world and significantly encourage accelerated soil erosion. Repeated tillage with heavy machinery destroys soil structure, pulverizing soil particles into dust that iseasily swept up by wind or water runoff. Fallow rotations, common with cash crops around the world and subsidized in bio-fuel production in the U.S., leave land vulnerable to the full force of wind gusts and raindrops. Monocultures tend to be planted in rows, exposing the soil between to erosion, and are commonly associated with fallow rotations. More and more marginal land, land that is steep and particularly susceptible to water erosion, is being planted by farmers either attracted by higher crop prices or forced by loss of productivity on flatter, but already eroded lands. In an increasingly complex global food web, seemingly separate causes of erosion begin to influence each other, magnifying their effects. For example, deforestation of tropical forests in Brazil clears the way for industrial soybean production and animal grazing to feed sprawling urban populations in the U.S. All the while, fertile topsoil is carried away by wind and water at alarming rates. Environmental harms resulting from accelerated erosion are well documented. Decreased soil fertility and quality, chemical-laden runoff and groundwater pollution, and increased flooding are just a few of these detrimental effects. There are, in addition, disproportionate social harms resulting from high rates of erosion that are less obvious, but no less directly linked. Hunger, debt, and disease are serious problems in mostly poor, rural communities around the world that are exacerbated by accelerated erosion.
As global agricultural development and trade have accelerated in the last half-century, mainly via the “green revolution” and the formation of the World Trade Organization , increasing trade pressures have raised export crop production in less developed countries. As a result, farmers mainly in Asia, Latin America, and sub-Saharan Africa are increasingly abandoning traditional farming techniques and locally significant crops in favor of adopting the industrial practices mentioned above that lead to high rates of erosion.5 While development institutions and governments proclaim concerns for the rural environment, agricultural policy supporting high commodity prices and limited credit access continually pushes farmers to intensify land use. Coupled with the fact that the total area of arable land in cultivation in these parts of the world is already very high , land degradation by soil erosion threatens food security by removing from cultivation land sorely needed for domestic food production. The majority of the world’s 868 million undernourished people live in Eastern and Southern Asia and sub-Saharan Africa. One of the international responses to soil degradation in the developing world has been to promote soil conserving tillage practices known as minimumor no-till agriculture. No-till agriculture protects soil by leaving crop residue on the field to decompose instead of plowing it into the ground before planting the next crop. Weed management is addressed with heavy herbicide use to make up for the loss of weed control from tillage. The practice, extensively adopted in the U.S., weed dryer has been popular in Brazil and Argentina, and much effort is being expended to expand no-till to Asia and Africa. There are, however, costs associated with no-till agriculture, both economic and social. First, no-till agriculture is expensive to adopt. Herbicides, seed drills, fertilizers, and other equipment require a high initial investment not possible for poor farmers without incurring significant debt. Second, heavier herbicide use increases human exposure to chemicals and contributes to water and air pollution. Third, weed pressures can change in unexpected ways as reliance on a handful of herbicides breeds resistance. Weed resistance to the popular herbicide, glyphosate, is an increasing concern in conventional agriculture and is leading to development of more harmful herbicides to compensate for glyphosate’s reduced effectiveness. Lastly, no-till agriculture also promotes monoculture cropping systems that, as described above, have a deleterious effect on soil quality. The techniques illustrated in this manual emphasize long-term soil stewardship using an integrated approach to soil health and management. For example, cover crops hold soil aggregates together in the wet season, protecting soil from the erosive effects of rain. Properly timed tillage limits its destructive effects on soil particles and soil structure. Compost promotes a healthy soil ecosystem, improving soil’s structure and its ability to more successfully withstand wind and water erosion. In addition to environmental benefits, agroecological systems are often based on traditional farming practices that promote soil-conserving techniques and varietal choices adapted to the particular region, stemming the tide of land consolidation and commodity crop production. Food security is enhanced and debt risk reduced by way of diverse cropping systems and labor-intensive, rather than input intensive, production methods. And there are public health benefits from eliminating exposure to harmful pesticides and herbicides. In sum, the serious challenge presented by accelerated soil erosion coupled with the uncertainty about whether no-till agriculture’s benefits outweigh its harms underscores the importance of employing an agroecological approach to farming that prevents soil erosion on farms.On vegetable farms in the Salinas Valley, a shrinking farm labor pool and rising minimum wages are driving innovation and adoption of machinery that can automate manual labor tasks — thinning, weeding and, for some crops, harvest. The technology is evolving quickly, led mainly by small engineering firms collaborating with large growers. Automation promises a number of benefits. Foremost, of course, is a reduced dependence on manual labor. But it could help in other ways too — for instance, automated weeding could remedy the declining effectiveness of some herbicides. UC researchers and advisors are helping to advance the basic technologies involved, and also serving as key evaluators of the technology . But the drive to automate also raises decades-old concerns about UC contributions to new technologies that are likely to primarily benefit only large-scale growers, at least in the short term.The automation of thinning and weeding involves two main steps: identifying each plant to be removed and then directing the killing of the undesired plant with a blade or a small dose of herbicide. It replaces work that would otherwise be done by hand with hoes. Figures on the acreage being thinned by machine aren’t available, but the use of automated thinners in some crops, notably lettuce, has been expanding in the Salinas Valley since its introduction in 2012 . The two in widest use in the Salinas Valley, according to several researchers and equipment suppliers, are made by two small northern European firms, Denmark-based F. Poulsen Engineering and Netherlands-based Steketee. Long-running concerns about farm labor cost and availability in Europe have driven automation innovation, and the technology has been more widely adopted there than in the United States, said Richard Smith, a UC Cooperative Extension farm advisor in Monterey County. While the weeding machines are costly — roughly $150,000 to $200,000 — their use appears to be limited more by availability than by price, according to equipment suppliers and UCCE staff. Poulsen and Steketee are small operations with limited production capacity. Britton Wilson of Pacific Ag Rentals, an equipment supplier to Salinas Valley farms, estimated that there are 15 to 20 Poulsen weeders in the United States, a figure Poulsen corroborated. “I’d love to get my hands on more” to meet local demand, he said.A crop like lettuce or broccoli represents a comparatively small market for major farm equipment makers like John Deere and Case IH. About 300,000 acres of lettuce are grown in the United States, for instance, compared with 12 million acres of cotton or 90 million acres of soybeans. As a result, vegetable crop automation is being led by small engineering and fabrication firms as well as growers themselves, often in close collaboration, said Mark Siemens, an associate specialist and associate professor of agricultural and biosystems engineering at the University of Arizona. Because the technology is somewhat modular, it’s possible to address the needs of a particular crop or grower by combining or modifying existing technologies and equipment. An example: Harvest Moon Automation, a four employee engineering firm with several clients in the Salinas Valley, recently received a patent on a modified version of a leafy greens harvester developed in partnership with two Salinas Valley growers. Steve Jens, Harvest Moon’s president, said the new machine uses a camera and pattern-recognition technology to spot foreign objects and diseased or damaged plants as the harvester moves across a field.