Increasingly, people are tuning in to the detrimental effects of pesticides and switching to organic produce – whenever possible and financially feasible. To that end, greenhouse tomatoes, cucumbers, and peppers seem pretty ideal. Available year-round, they are usually unblemished, grown hydroponically, need few pesticides, and are even grown locally. Great. Except for one thing. When the weather conditions are right, a ghastly orange glow suffuses the sky – from the greenhouses 20 miles away. That’s a whole lot of light.
Canada has experienced a huge boom in greenhouse techniques, including flowers and vegetables. The main vegetable crops are tomatoes, cucumbers, lettuce, and peppers. Increasingly, hothouse tomatoes are exported to US, as well as supplying national demand. Hydroponic agriculture uses growth media, such as rockwool and liquid nutrients, rather than traditional soil. Pests are controlled with biological techniques – adding ladybugs to eliminate aphids, for example. Plants are encouraged to grow vertically, allowing for increased productivity and efficient use of space.
However, there are some problems lurking under the surface of these ideal vegetable incubators. In BC, home to a large number of glass greenhouses, extra light is needed to compensate for overcast days. But using screens to hold in the light also produces too much heat – so the light is allowed to escape through the windows. Not to mention the fact that greenhouses are located on agricultural land, occupying but not using otherwise fertile soil.
Energy costs are another consideration. Ensuring year-round growth is energy intensive, requiring power for heating and lighting in the winter months, and often cooling in the summer, along with irrigation and CO2 supplementation. Computerized controls direct temperature, moisture, and nutrient addition. It adds up to a high need for energy, most of which comes from fossil fuels such as natural gas, coal, and oil. In 2006, total sales of Canadian greenhouse products amounted to $2.3 billion, while fuel costs were $278 million.
So what are the alternatives? One intriguing modification in Ontario is a soap-bubble insulated greenhouse, which uses solar heating rather than fossil fuels. Thermal blankets are used in some locations, but are better for keeping in heat with frigid temperatures outside. Geothermal heat sources are another possibility.
Greenhouses should be able to modulate the use of light – shielding plants from excess sunlight that can burn leaves, for example. So why isn’t there more awareness of unnecessary light? All that glow in the sky is wasted light – and wasted energy. It is also light pollution, to the detriment of professional and amateur astronomers – as well as preventing local residents from even seeing the stars in the sky. There are also concerns that extensive artificial lights interfere with different animal species, from migrating birds to feeding bats. With recognition of the problem, creative solutions are desperately needed.
