Climatic Changes and Wetlands in Higher Latitudes

Numerous ecological services provided by a system tend to change over time, thus, making it tougher for policy makers/managers to evaluate trade-offs while estimating the cost-benefit analysis. Learning the resilience, threshold level and lag times allows us to gauge the strength and weakness of our technological advances and policies that might help us to cope with nonlinear impacts of global climatic change in ecosystems such as freshwater wetlands. Aquatic ecosystems can be very sensitive to changes induced by global climate change, e.g., water quality and quantity, and temperature. Thus, any mitigating strategies should try to take into account the nonlinear behaviors of the ecosystem processes and components, and begin planning to minimize effects of the changes.

Wetlands are found in many climatic zones ranging from tropics to tundra, and are some of the most productive ecosystems on the earth. The roles wetlands play ranging from carbon (C) sequestration to flood control and biodiversity protection are immense. Various physico-chemical and biological characteristics of wetlands regulate cycles of nutrients including carbon (C), nitrogen (N) and phosphorus (P). Although wetlands are significant sources of the global methane (CH4) emissions, they have the highest C density among terrestrial/semi-aquatic ecosystems and relatively greater capacity to sequester additional carbon dioxide (CO2) through organic matter accretion. Wetlands sequester C through high rates of organic matter inputs and reduced rates of decompositions. Carbon dioxide and CH4 along with nitrous oxide (N2O) comprise about 90% of direct radiative forcing of long-lived greenhouse gases [1].

The wetlands in higher latitudes are particularly important because of their high productivity, and potential to store large amounts of organic C in biomass and accreted organic matter. However, they could become massive sources of greenhouse gases such as CO2 and CH4 due to changes in hydro-climatic conditions because of global rise in temperature. The global warming not only has direct impacts on such wetland ecosystems, but it may also exacerbate positive feedback loop by putting more greenhouse gases into the atmosphere [2].

Depending on environmental conditions, stored nutrients and other contaminants could be released from organic matrix via mineralization and recycled through the ecosystems or exported from them. A major portion of detrital matter is buried via accretion in wetlands, which may serve as a long-term storage of C, as well as P. However, the expected hydro-climatic changes in the coming decades due to global rise in temperature could substantially mineralize the organic matter and supply a large amount of P to the water column, hence cause the disruption of the ecosystem. Phosphorus is often a limiting nutrient and a primary controller of eutrophication. Once the external loads are curtailed, internal nutrient regeneration resulting from decomposition of enriched detrital tissue and soil organic matter to a large degree could determine the productivity and water quality of a wetland. Several physico-chemical and biological transformations in the soils and water column may result in the breakdown of detritus and organic matter in wetlands, as well as global rise in temperature can also change the composition of aquatic/semi-aquatic communities, in turn, could lead to adverse effect on human food chain to disruption/ collapse of the ecosystems.

Wetlands may retain undisturbed organic matter for thousands of years, however, localized changes in hydro-climatic patterns may alter physical and chemical nature of the organic matter and release bound nutrients. Responses of ecological systems to changes in the physical climate system sometimes are not linear, but they are inherently nonlinear as in the case of complex ecosystems, thus, adaptive ecosystem management should include understanding and anticipation of nonlinear dynamics [3].

Direct economic benefits dominated policies in many parts of the world often disregard the indirect ecological services provided by an ecosystem, while estimating cost-benefit analysis. Such policies not only change the localized environment for the immediate future but also contribute to long-term changes, e.g., hydro-climatic changes and the global rise in temperature. Researchers have been successfully demonstrating a fundamental understanding of eutrophication processes in freshwater wetlands, but they are less successful in communicating what it takes to reverse the wetlands to the original conditions [4]. Moreover, various studies have been conducted to determine effects of climate change in C sequestration in wetlands [5], however, studies on P dynamic in wetlands as affected by changes in levels of temperature and water are limited. Thus, augmenting limnological data can offer the needed evidence for the control of P inputs [6], as well as provide insights on possible ways for interventions, which helps to control eutrophication and subsequent disruption/ collapse of the ecosystem.

In conclusion, consequences of hydro-climatic changes such as temperature and water level, and their influence on localized microenvironments may trigger the excessive influx of various nutrients, including P to the these wetlands. Determining the extent of P mineralization under changing conditions would be crucial, thus it demands in-depth study. Identification and estimation of nonlinear behaviors in the stability and bioavailability of organic P compounds, which are present in the water columns, detritus and soils, at different temperatures and water levels, in light of potential change in hydroclimatic conditions will allow quantification of processes controlling P cycling in wetlands. Wetlands are often viewed as sinks for P, because of their capacity to transform inorganic P into organic P. However, the short-term storage does not guarantee acceptable water quality, especially under changing levels of stressors as affected by hydroclimatic conditions. The critical question is not how much P is stored in a wetland, but how the resilience and nonlinearity as related to stability of the stored P are affected by the levels of environmental stressors that are expected to fluctuate in the decades to come. Addressing how stable organic P is, and at what threshold level and lag time would organic P behave nonlinearly and release back into the water column for uptake is crucial. The relationships need to be developed between P mobilization processes, temperature and water levels in wetlands to get valuable insights to formulate wetland management/protection strategies to increase resilience of wetlands, in turn, ascertain continuous goods and services from these wetlands such as carbon sequestration.