Printer-friendly version
By Vasyl CherlinkaApril 18, 2024 (San Diego) – San Diego County’s agriculture is a rich tapestry of over 5,000 mini-farms seamlessly blended into expanding urban landscapes. Most are family-owned organic farms producing high-value crops on just a few acres of land to turn a profit in this water-scarce, highly urbanized region. The moderate climate, ample sunlight, and varied terrain made the area perfect for cultivating an astonishing variety of 200+ commodities, ranging from strawberries and citrus to avocados.
Today, San Diego is the No. 1 nursery crop producer and the 12th-largest agricultural economy in the U.S. It also outperforms its fellow top-producing counties within California in terms of average dollar value per acre.
On the downside, as climate change effects become increasingly felt in the region, this places an enormous strain on local agricultural producers.
How climate change affects San Diego County’s agriculture
While San Diego County and California are making strides in cutting greenhouse gas emissions (GHGs) – the primary anthropogenic driver of climate change – to reach the target of 80% lower emissions from the 1990 baseline by 2050, the annual maximum and minimum temperatures are expected to steadily rise even in the best-case scenario. The resulting increased dryness, erratic rainfall patterns, and more frequent and intense weather extremities will inevitably affect agricultural commodities.
- Rising temperatures: Heat-adverse specialty crop types (for example, lettuce and strawberries), which prefer mild coastal temperatures, are likely to be the worst hit – especially in urban and semi-urban farms exposed to additional warming through the “heat island effect”. Heat waves may cause heat drop and defoliation and affect fruit quality in perennial tree crops; many fruit and nut trees will suffer from the lack of “chill hours”. The heat-loving citrus and subtropical avocados may benefit from warmer winters; however, some studies project a decline in avocado yields when exposed to higher summer temperatures. The irrigation water needs of vegetable and ornamental crops will increase, while the produce quality will likely decline.
- Irregular precipitation patterns: Southern California is bound to maintain its status as a region with the highest year-to-year precipitation variability in the continental U.S., with rainfall patterns growing less frequent but more intense. Winters will grow wetter, while springs and autumns will get dryer, accompanied by more frequent, severe droughts. The drastically varying rainfall will likely drive more extreme precipitation events (coastal storms, flash floods, mudslides), threatening steep farmland in inland valleys. Even in years with above-normal precipitation coming from storms, water access will decrease, further exacerbating San Diego’s water crisis.
Stronger wildfires: The frequency and scale of wildfires inherent to San Diego County's climate are projected to increase, fueled by climate change-driven drier conditions that reduce plant and soil moisture. The central third of the county, with sparse development and dense fire-prone vegetation (such as chaparral), is at the highest risk. Precipitation variability and shifting seasons may result in a later and more intense fire season driven by infamous Santa Ana winds.
- Thriving pests and weeds: Higher temperatures year-round create more favorable conditions for the activity and reproduction of arthropod pests, foreshadowing progressively severe and frequent outbreaks soon. Additionally, increased exposure to heat makes plants more susceptible to pests and renders insecticides less effective. The county may also see increased populations of rodents, especially as winters grow warmer. Climate change will alter the weed growth and spread patterns, favoring drought-tolerant species through hotter, dryer conditions and increased herbicide resistance. Regular tailored weeding in drought years will deter weed outbreaks when rainfall returns.
Building climate resilience on farms through sustainable practices
One of the most dramatic climate change effects that San Diego County is already witnessing is “hydro-climate whiplash” – sudden shifts between overly dry and wet weather. As the climate heats up, these swings will intensify. So, while some agricultural regions have to adapt to either drier and hotter or wetter growing conditions, San Diegans are getting the worst of both worlds.
Despite numerous agricultural challenges, climate-resilient farming stands as a beacon of hope. Encompassing a range of sustainable practices, it either strengthens a farm’s climate resilience or harnesses its capacity to mitigate climate change. Let’s explore some of the most effective methods gaining traction in San Diego.
Efficient crop rotation & crop diversification
Thoughtful expansion of the range of crop types cultivated simultaneously or in a set order may strengthen the farm’s economic and environmental resilience. In this way, farmers can not only spread financial risks related to adverse weather but also improve soil health (acting as a shield against pests, weeds, and diseases), structure (improving water-holding capacity and erosion resistance), and soil’s capacity to sequester carbon dioxide, which altogether can positively impact farm’s productivity. By including drought- and salt-tolerant types of crops into their crop rotation schemes, San Diego growers can secure better crop production under increasing scarcity of irrigation water and rainfall.
Despite plentiful benefits on the horizon, the County’s expensive land may discourage smallholder farmers from giving up intensive high-value monocultures in favor of diversified cropping that can be less profitable per acre. The government incentives for climate-smart crop diversification could be the solution in the long run. Overseeing a county- or statewide project entails using accurate monitoring tools and historical farm data, as crop rotation choices largely depend on current and previous cropping years. Crop classification using satellite images allows identifying crops remotely and on a large scale, considerably saving budgets and improving the accuracy of resulting crop type maps, which provide vital information for informed crop management decisions.
Sustainable water managementDespite a relatively low water consumption by San Diego County’s agriculture and a 20% decrease in statewide water use over the past two decades, there is still a need and room for water conservation improvement. Local farmers have been actively employing various climate-resilient irrigation methods leveraging a tailored approach that allows calibration of water amounts based on an array of data, including evapotranspiration rates, effective precipitation, soil moisture, irrigation amounts received, and sensitivity of various types of crops grown to drought stress to name a few.
For example, a small family-owned Bantle Avocado Farm located in Fallbrook uses a wireless mesh network to irrigate its avocado, lemon, and olive trees based on data from in-ground soil moisture sensors. This system delivers water precisely where and when needed to maximize every drop.
Another failproof method is micro-drip irrigation, which delivers water close to plant roots, minimizing evaporation and maximizing crop uptake. San Diego crop growers are increasingly transitioning from old-fashioned and unsustainable watering to micro-sprinklers, conserving more water per acre and reaping bigger harvests. One local citrus grower reported a drop from 9 to 6 acre-feet of consumed water after switching from flood irrigation to micro-drip. With container-grown ornamental crops, micro-drip holds the potential for tangible water savings as opposed to hand watering; challenges related to its use are outweighed by potential benefits – reduced water, hand labor, and fertilizer costs.
Boosting soil health and carbon sequestration
Fully leveraging the largest terrestrial carbon sink at our disposal – the soils – to reduce GHG emissions, improve soil health, and provide additional income to growers is the core idea behind carbon farming. Sustainable management of agricultural farmland builds soil health, and the benefits are plenty: better soil structure, richer soil microbiota and organic matter, more robust tolerance to droughts and floods, and higher capacity to store carbon and hold moisture. To San Diego County, committed to going carbon-neutral by 2035, this looks like a prospective solution for offsetting some of the harm done by the largest GHG emitter – the transport industry – while securing future food availability by growing in more resilient soils.
Minimizing soil disturbance by switching from intensive conventional soil management (e.g., heavy tillage) to regenerative, more sustainable ones is a shortcut to improving soil health and promoting carbon sequestration. Typical soil-benefiting practices include mulch/compost application, reduced or zero tilling, and cover cropping.Farmers at the non-profit Coastal Roots Farm in Encinitas create their own compost by rotating crops and chickens through fields, building rich soil organic matter, and growing organic vegetables, herbs, fruit, and flowers.
Visionary farmers at Pauma Valley have set up various initiatives and projects, such as the Carbon Farming Task Force or Carbon Sink Demonstration Farm, to showcase the potential benefits of carbon farming and encourage the community and government to tap into them. The joint 5-acre farm project by Solidarity Farm and the Pauma Band of Luiseno Indians showed a 4.4% increase in soil organic matter and a 3% increase in stored carbon – a result achieved through no-till, compost application, switch to perennial crops, cover cropping, and installing windbreaks and hedgerows to attract pollinators. Another similar 80-acre project attested to the improved water-holding capacity: every 1 percent of soil organic matter built up in the process can save an acre-foot of water.
Minding biodiversity and preserving local ecosystems
San Diego County is a biodiversity hotspot with the greatest species diversity across the continental U.S. Due to climate change and urban expansion, preserving the region’s natural habitats and ecosystems calls for increased conservation efforts, and agriculture can play a significant role in it.
San Diego County farmers can implement a range of practices that support biodiversity and provide habitats for native species. Installing windbreaks, hedgerows, and flowering perennials can increase populations of bird and insect species that predate on pests while also creating habitats for pollinators. Riparian restoration can support multiple bird species, including migratory and endangered ones, decrease nutrient and sediment runoff, and promote carbon sequestration. Through integrated pest and weed management, growers can reduce the environmental footprint of pesticide and herbicide use by employing eco-friendly practices to break pest and weed cycles.
Ramona Ranch Winery in Ramona – the first and only Certified Sustainable winery with a Certified Wildlife Habitat – is a vivid example of how being mindful of nature pays off. By planting an insectary of native plants, planting bird and butterfly zones, installing owl boxes, and maintaining riparian habitats in their vineyard, they’ve established a harmonious, symbiotic relationship with wildlife. Apart from nurturing biodiversity, the crops and vineyard are sustainably managed through hand labor, low-volume drip irrigation, composting, and cover cropping which results in superior wine production. By elaborating a holistic approach to target the entire scope of challenges induced by climate change and receiving broader agency support, San Diego County stands a good chance of not only making its agricultural sector resilient in the face of severe weather calamities but also transforming it into a powerful mitigation tool that helps offset carbon emissions and conserve the dwindling natural resources.
Vasyl Cherlinka is a Doctor of Biosciences specializing in pedology (soil science), with 30 years of experience in the field. With a degree in agrochemistry, agronomy and soil science, Dr. Cherlinka has been advising on these issues in the private sector for many years
Recent comments