Altered biogeochemical cycles together with climate change increase the vulnerability of biodiversity, food security, human health, and water quality to changing climate. However, natural and managed shifts in major biogeochemical cycles can help limit rates of climate change.

This finding is from chapter 15 of Climate Change Impacts in the United States: The Third National Climate Assessment.

Process for developing key messages: The key messages and supporting text summarize extensive evidence documented in two technical input reports submitted to the NCA: 1) a foundational report supported by the Departments of Energy and Agriculture: Biogeochemical Cycles and Biogenic Greenhouse Gases from North American Terrestrial Ecosystems: A Technical Input Report for the National Climate Assessment,6b1b7945-4773-4923-8a45-3dc034dff5f8 and 2) an external report: The Role of Nitrogen in Climate Change and the Impacts of Nitrogen-Climate Interactions on Terrestrial and Aquatic Ecosystems, Agriculture, and Human Health in the United States: A Technical Report Submitted to the U.S. National Climate Assessment.4b55a6d6-94ab-4ca9-abaf-e17bf9d86bc4 The latter report was supported by the International Nitrogen Initiative, a National Science Foundation grant, and the David and Lucille Packard Foundation. Author meetings and workshops were held regularly for the foundational report,6b1b7945-4773-4923-8a45-3dc034dff5f8 including a workshop at the 2011 Soil Science Society of America meeting. A workshop held in July 2011 at the USGS John Wesley Powell Center for Analysis and Synthesis in Fort Collins, CO, focused on climate-nitrogen actions and was summarized in the second primary source.4b55a6d6-94ab-4ca9-abaf-e17bf9d86bc4 An additional 15 technical input reports on various topics were also received and reviewed as part of the Federal Register Notice solicitation for public input. The entire author team for this chapter conducted its deliberations by teleconference from April to June 2012, with three major meetings resulting in an outline and a set of key messages. The team came to expert consensus on all of the key messages based on their reading of the technical inputs, other published literature, and professional judgment. Several original key messages were later combined into a broader set of statements while retaining most of the original content of the chapter. Major revisions to the key messages, chapter, and traceable accounts were approved by authors; further minor revisions were consistent with the messages intended by the authors.

Description of evidence base: The author team evaluated technical input reports (17) on biogeochemical cycles, including the two primary sources.4b55a6d6-94ab-4ca9-abaf-e17bf9d86bc4 6b1b7945-4773-4923-8a45-3dc034dff5f8 The climate–biogeochemical cycle link has been demonstrated through numerous studies on the effects of reactive nitrogen and phosphorus on forest carbon uptake and storage, and decomposition of organic matter;c744676f-c7f4-404e-96f9-cfc0dbbf8445 30bebfa7-9079-4265-a95e-f078adf7402b c4ec73f8-97df-4dde-a6da-9ca3615b2cf3 temperature effects on ecosystem productivity;8d1b0aac-420e-497e-8372-d7865ace46a3 71db3320-3141-4271-9b9a-24e9570ede5a c1c68aa1-23cd-4a29-843a-c9d609a2efe0 and sensitivity of natural methane emissions to climate variation.1edf49ce-5f68-4b5a-86b1-a9770d401acc Where the nitrogen and phosphorus cycles are concerned, a number of publications have reported effects of excess loading on ecosystem processes756b315a-6ec9-4b27-b521-f2b91f2c28bc 93b197da-f279-4576-8ce5-0622240638e2 ed33d4a4-ff1f-4351-8225-03f3a647290b and have projected these effects to worsen.93b197da-f279-4576-8ce5-0622240638e2 6ceb89b3-adf0-4486-b4dc-64fc5f4f0079 13dd233a-3dcf-44fd-b31b-c1f433330039 Additionally, studies have reported the potential for future climate change and increasing nitrogen and phosphorus loadings to have an additive effect and the need for remediation.7bb29bb1-926d-4367-aa10-d15808b296b3 93b197da-f279-4576-8ce5-0622240638e2 The literature suggests that co-benefits are possible from addressing the environmental concerns of both nutrient loading and climate change.4b55a6d6-94ab-4ca9-abaf-e17bf9d86bc4 a65e5260-d143-49dd-b20e-c0fefddbef70 afbd60ab-ba9f-4547-88e3-968bc3a4b949 76f06851-57c9-4e6e-b9f2-268849aeb233 d809f14b-29ae-49f0-ba12-bd4674e1556c

New information and remaining uncertainties: Scientists are still investigating the impact of nitrogen deposition on carbon uptake and of sulfur and nitrogen aerosols on radiative forcing. Recent work has shown that more than just climate change aspects can benefit from addressing multiple environmental concerns (air/water quality, biodiversity, food security, human health, and so on)

Assessment of confidence based on evidence: High. We have a high degree of confidence that climate change will affect biogeochemical cycles through its effects on ecosystem structure and function (species composition and productivity). Similarly, there is high confidence that altered biogeochemical cycles will affect climate change, as for example in the increased rates of carbon storage in forests and soils that often accompany excess nitrogen deposition.

References :

• Impact of nitrogen and climate change interactions on ambient air pollution and human health (76f06851)
• Phosphorus control is critical to mitigating eutrophication (756b315a)
• The Role of Nitrogen in Climate Change and the Impacts of Nitrogen-Climate Interactions on Terrestrial and Aquatic Ecosystems, Agriculture, and Human Health in the United States: A Technical Report Submitted to the US National Climate Assessment (4b55a6d6)
• Simultaneously Mitigating Near-Term Climate Change and Improving Human Health and Food Security (a65e5260)
• Soil warming, carbon-nitrogen interactions, and forest carbon budgets (c744676f)
• Agricultural legacies, food production and its environmental consequences (d809f14b)
• Coupled biogeochemical cycles: eutrophication and hypoxia in temperate estuaries and coastal marine ecosystems (93b197da)
• Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years (1edf49ce)
• Impacts of climate warming on lake fish community structure and potential effects on ecosystem function (6ceb89b3)
• Eutrophication science: where do we go from here? (ed33d4a4)
• Reduction of forest soil respiration in response to nitrogen deposition (30bebfa7)
• Global change and eutrophication of coastal waters (13dd233a)
• The interactive effects of excess reactive nitrogen and climate change on aquatic ecosystems and water resources of the United States (7bb29bb1)
• Recent patterns and mechanisms of carbon exchange by terrestrial ecosystems (71db3320)
• Effect of climate change on air quality (afbd60ab)
• Effects of elevated carbon dioxide and increased temperature on methane and nitrous oxide fluxes: evidence from field experiments (8d1b0aac)
• Nitrogen Additions and Litter Decomposition: A Meta-Analysis (c4ec73f8)
• Responses of terrestrial ecosystems to temperature and precipitation change: a meta-analysis of experimental manipulation (c1c68aa1)
• Biogeochemical Cycles and Biogenic Greenhouse Gases from North American Terrestrial Ecosystems (6b1b7945)