Agriculture and Ecosystems
As temperatures rise over the next century, summers and falls in the Northeast will become hotter and growing seasons will lengthen. Changes in precipitation patterns, drought incidence, and sea level rise will also affect crops, livestock, forests, and wildlife.
Warming temperatures are projected to increase drought risk, which endangers crops as well as livestock, and increases the risk of wildfire in forests. Heat waves can also have a negative effect on crop yields and milk production.
At the other extreme from too little water is too much water. Heavy precipitation events—which are projected to increase in frequency, duration, and intensity—can cause direct crop damage. Heavy rains also increase soil moisture levels, which can delay spring planting and subsequent fall harvests, and may reduce yields.
Longer growing seasons and warmer winters are associated with increased weed and pest pressure, as species emerge earlier and in greater numbers. Additionally, aggressive weeds—such as kudzu—benefit from increased atmospheric carbon dioxide levels more than crop plants do; increased carbon dioxide can also help weeds become more resistant to herbicides. Paradoxically, warmer winters can increase frost and freeze damage. For example, when a warm period in late winter or early spring causes premature leaf-out or bloom, crops are susceptible to damaging frost events.
In Northeastern forests, changes in species distributions by elevation has already been observed: wildflowers and woody perennials are blooming earlier, and migratory birds are arriving sooner than they did in the past. Some bird species have expanded their ranges northward, as have some invasive insect species. As ecosystems change due to warming temperatures, temporal mismatches can occur between key food sources and migration patterns, increasing vulnerability of both ecosystems and species. The expansion of insect pests, pathogens, and invasive plants into new habitats may result in an overall loss of biodiversity, function, and resilience in some ecosystems.
Rising sea levels also threaten the Northeast's coastal ecosystems through erosion of beaches and dunes and loss of marsh coverage. Projections for warmer ocean temperatures are expected to result in northward shifts of commercially important fish and shellfish. Suitable ocean habitats will shrink for some species and expand for others, but it is difficult to predict which species will be able to move and adapt as climate zones shift. Warmer temperatures can also influence growth rates and the timing of seasonal migrations. In 2012, for example, lobsters in the Gulf of Maine started their summer migration a month early and grew to market size faster than usual. The result was a saturated market and a price collapse for Maine lobstermen. In many communities that depend on fishing and tourism, climate-related changes can cost jobs and disrupt traditional ways of life.
The preceding text is excerpted and abridged from Climate Change Impacts in the United States: The Third National Climate Assessment (Chapter 16: Northeast) and from the NOAA Technical Memorandum NOAA Fisheries Climate Science Strategy (NMFS-F/SPO-15).
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