Climate change and deltas -- seminar in Italy, 8-9 October 2003
Malheureusement, il n'y a pas de version française de ce document.
"Climatic change and foreseeable impacts on deltas: a new challenge for the conservation of protected areas"
Comacchio, 8 October 2003 - Delta chiama Delta Association/MedCoast
Climate change and wetlands: impacts, adaptation, and mitigation
by Dr Tobias Salathé, Convention on Wetlands
Ramsar Bureau, 28 rue Mauverney, CH-1196 Gland, Switzerland, email@example.com
This presentation conveys some key messages elaborated over the last few years by the contracting parties (currently 138 countries throughout the world) to the Convention on Wetlands (adopted in Ramsar, Iran, 1971). So far, managers of water and protected areas have paid little attention to the expected impacts of climate change on future water resources and the consequences for the management of downstream wetland ecosystems. However, climate change is here and will be with us for a long time to come. We are faced with a great destabilization and reshuffling of the world's hydrological systems. The data and assumptions used in the past are no longer valid for the future. We will have to live with a greater uncertainty arising from climate change.
Goods and services that wetlands provide
Wetlands, i.e. marshes, fens, peatlands, rivers, lakes, lagoons and coastal aquatic ecosystems, provide goods and services essential for the survival of humans such as: food, fibre, clean water, clean air, carbon and other nutrient stores or sinks, flood and storm control, groundwater recharge and discharge, pollution control, organic matter or sediment export, biodiversity, pollination, routes for animal and plant migration, landscape and waterscape connectivity, aesthetic, spiritual, cultural and recreational services. These all contribute to human health and wellbeing.
The role of wetlands in global biochemical cycles
Terrestrial wetlands have a major role in the carbon, nitrogen and sulphur cycles. All these cycles are driven by the hydrological (or water) cycle. Since the 1750s, human activities, e.g. burning fossil fuel and land use change, have increased the atmospheric concentrations of greenhouse gases (e.g. water vapour, carbon dioxide, methane, nitrous oxides) and thus affected all these cycles. Increase in greenhouse gases has and will continue to increase the mean surface global temperature and enhance the global hydrological cycle resulting in more extreme and heavier precipitation events in many areas with increasing precipitation. Atmospheric concentrations of carbon dioxide have increased by about 30% and methane by about 150%. Nitrogen production, due to chemical fertilizer production, has doubled in the 20th century and atmospheric concentrations of nitrous oxide have increased by about 16%. Sulphur dioxide emissions, which have a cooling effect on the atmosphere and are generally short lived, have increased. However, in the late 1990s, the anthropogenic sulphur dioxide emissions have decreased due to structural changes in the energy system as well as concerns about local and regional air pollution.
The concentration of CO2 in the atmosphere, along with nitrous oxide, has acted as a fertilizer and has affected the uptake of carbon by some terrestrial ecosystems, including wetlands. Peat accumulating wetlands are especially important in the carbon cycle because of the large carbon store accumulated in them over millennia. With projected climate changes and associated land use and land cover changes, these carbon stores are at risk of being released to the atmosphere. Besides being carbon sinks, wetlands are sources of methane to the atmosphere. Most wetlands are highly sensitive to hydrological changes, especially at the level of their water catchment, and thus changes in hydrology - e.g. through drainage, fires or climate change - could lead to further changes in the carbon stores.
Impacts of climate change on wetlands
Climate change can directly or indirectly affect many ecosystem functions and thus the goods and services they can provide. Some of these impacts are:
- A potential for significant disruption of ecosystems productivity and decomposition.
- Increasing CO2 concentrations in the atmosphere increasing net productivity in vegetation systems, causing carbon to accumulate in vegetation over time.
- Increased risk of extinction of vulnerable species for very minimal changes in climate.
- Impacts induced by climate change where weather-related disturbance regimes and nutrient cycling are primary controls on productivity.
- Reduced average annual water runoff in some areas, and increased annual runoff in others, affect many ecosystem functions. In snowmelt dominated watersheds, earlier snowmelt and a smaller proportion of winter precipitation falling as snow is projected to shift peak river flows toward winter from spring and may thus change the phenology of many species.
- Climatic change and other pressures make small inland waters vulnerable that are downstream from many human activities.
- Peatlands underlain by permafrost could become net carbon sources rather than sinks. With climate warming, drainage of tropical peatlands could lead to increased risk of fires and affect the viability of tropical wetlands.
Examples of projected changes due to sea level rise and climate change include:
- Many coastal systems will experience increased levels of inundation and storm flooding, accelerated coastal erosion, seawater intrusion into fresh groundwater, encroachment of tidal waters into estuaries and river systems, elevated sea surface temperatures and ground temperatures prevailing wave activity and storm waves and surges.
- Sea level rise of about half a meter would inundate significant portions of some small, low lying islands and their coastal ecosystems. Resources critical to island societies and economies such as freshwater, fisheries, coral reefs and atolls, beaches and wildlife habitat would be adversely impacted.
- Adverse impacts on coral reefs through increased bleaching and reduced calcification rates due to higher carbon dioxide levels and increased sea water temperatures.
- Traditional indigenous societies in coastal areas and/or small islands are vulnerable due to their dependence on climate sensitive resources four subsistence hunting and gathering and sometimes low capacity to adapt to changes in the productivity, abundance or geographic distribution of these resources.
- A number of marine mammal and bird species may be adversely affected as they are dependent on coastal fish that are sensitive to inter-annual and longer-term variability in oceanographic and climatic parameters.
- Migratory bird populations that rely on suitable foraging habitat whilst en-route and or those dependent on coastal sites for nesting may be adversely affected by climate.
Extreme climatic events have and will continue to have major impacts on wetlands; examples include:
- Projected higher maximum temperatures, more hot days and heat waves could lead to increased heat stress and increased susceptibility to pest and disease attack in many wetland plants and animals.
- Projected increased summer drying over most mid-latitude continental interiors and associated risk of drought could lead to decreased water resource quantity and quality, physiological stress on animals and plants, decreased wetland productivity in some areas and increased risk of fires.
Impacts of potential changes in wetlands on climate change include:
- In the Arctic, changes in the extent of forests, grassland, shrubland, wetland and their boundaries could enhance projected regional warming.
- In semi-arid or arid areas without surface water, evapotranspiration and the albedo coefficient affect the local hydrological cycle; thus a reduction in vegetative cover could lead to reduced precipitation and change the frequency and persistence of droughts.
Human responses to climate change could further exacerbate the negative impact on many wetlands. For example, human responses to a warmer climate are likely to place greater demands on freshwaters to meet water needs for urban and agricultural use. This could potentially result in decreased flow in rivers and streams and greater fluctuations in water level. These changes would cause a loss of ecosystem services and products from some wetlands. Conflicts between developers and those wishing to reduce the development pressure on lakes and streams would likely intensify as freshwater becomes either more scarce or more abundant.
Difference between wetland types
Like any ecosystems, some wetlands can be considered to be resilient to climate change and others more sensitive, either because they are near their moisture or temperature tolerance and/or because their species and their functions have very narrow limits. Wetlands in high latitude and/or high altitude areas and coral reefs are considered to be amongst those most sensitive to climate change and thus are likely to be impacted earlier. In addition, an effect of intertia can be observed in several wetland ecosystems, e.g. due to the longevity of wetland species. This means that the impacts may not become apparent over a short period of time, but only with delay and in the longer term.
Other wetlands that could be impacted by climate change are those located in the continental interiors and downstream areas, likely to be influenced much by changes in their catchment hydrology. In near-shore marine and coastal systems, many wetlands could be impacted indirectly due to changes in storm surges and saltwater intrusions into freshwater systems.
Climate change vs other human pressures
The earth is being subjected to many human induced and natural changes, often referred to as global change. These include pressures from increased demand for resources, increase in human consumption patterns leading to land use change (including urbanization), accelerated rate of anthropogenic nitrogen production/deposition and other air pollutants, accelerated rate of biodiversity loss and climate change. The impacts of these pressures often lead to increased demand for access to land, water and wildlife resources. The result is a change in the state of the earth's land surface and in the landscapes where humans live and the goods and services humans receive from the ecosystems, at regional and global scales. The impacts of climate change include changes in atmospheric composition of greenhouse gases, temperature, precipitation and sea level rise. These can then affect disturbance regimes, such as frequencies of fires and outbreaks of pest/diseases.
Over the next two or three decades, the land use change resulting in drainage and clearance of wetlands, changes in their hydrology, are likely to dominate the changes due to projected climate change. However, changes listed above interact with each other and affect the ecosystem functions. For wetlands in particular, climate change is an added stress that would affect the hydrological regime, the biodiversity and thus many of the functions and goods and services provided by these ecosystems.
Options to adapt to climate change
Human adaptation options to climate change are dependent on institutional capacity and infrastructure. In general, the potential for adaptation is more limited for developing countries which are also projected to be the more adversely affected by climate change. Adaptation appears to be easier if the climate changes are modest and/o gradual rather than large and/or abrupt. Many of the adaptation options should not only address climate change impacts but could provide "win-win" solutions for other problems as well, e.g. wetland degradation. Adaptation options should be considered in a framework of sustainable development and should therefore not be in conflict with the wise use of wetlands. However, adaptation options have to take into account the inertia of some wetland species and functions, needing long-term planning and implementation, probably according to a 10-year cycle. Monitoring of adaptation measures should become an essential feature.
Most of the wetland processes are dependent on the hydrology of their water catchment. Thus, adaptations for the projected climate change have to be operational at catchment level. This may often be practically difficult or limited. There are a number of potential adaptation options contributing to the conservation and wise use of wetlands:
- Designing multiple-use protected areas which incorporate corridors that would allow for migration of organisms as a response to climate change.
- Expanding aquaculture to relieve stress on natural fisheries.
- Specific management in some ecosystems could reduce pressures on wetlands, e.g. in the Arctic. Economic diversion could reduce the pressure on wildlife, rotational use of marginal wetlands in semi-arid areas could wetland and wetland biodiversity loss.
- Integrated land, water and marine area management with the aim of reducing non-climate stresses could be beneficial to wetlands, e.g. reduction of fragmentation of water systems, of land-based pollution into coastal systems such as coral reefs or mussel banks.
- More efficient use of natural resources and restoration of degraded wetlands.
However, there are likely also to be negative repercussions of specific adaptation options to climate change, examples include:
- Active transportation of warm water-adapted aquatic species towards the poles could result in the extinction of local wetland species and large changes in ecosystem processes with economic consequences.
- Negative interactions resulting from increased stocking of species and from relocation of recreational and aquaculture endeavours.
- Negative effects related to secondary pressures of new hydrological engineering structures.
Options to use wetlands in mitigation greenhouse gas emissions
Between 1980 and 1998, the terrestrial ecosystems have been a small net sink for carbon dioxide, probably as a result indirect effects of human activities, including the CO2 fertilization effect and nitrogen deposition and possibly changing climate. Projections suggest that the additional terrestrial uptake of atmospheric CO2 on a global scale may continue for a number of decades but may then gradually diminish and could even become a source by the end of the 21st century. This conclusion does not consider the effect of future land use change or actions to enhance the terrestrial carbon sinks. In particular the Kyoto Protocol and the Bonn Accord allow carbon credits for afforestation. Reforestation could allow forested wetlands on land that has been without forest cover for a period of time. In particular:
- Reforestation benefits could include an increase in the diversity of flora and fauna, except where biologically diverse non-forest ecosystems, e.g. grasslands, are replaced by forests consisting of single or only few species.
- Avoiding deforestation can provide potentially large co-benefits, including conservation of biodiversity, soil resources and maintenance of non-timber forest products.
- Increasing three cover can improve and protect soil quality in vulnerable areas and stabilize watershed flows, thus benefiting wetland functions.
- One of the major sources of greenhouse gases methane and CO2 are peatland dominated wetlands. Actions that would avoid degradation of these wetlands and the potential release of these greenhouse gases would be an efficient mitigation option.
We need to make changes in our priorities for water and protected areas management and more effective dealing with risks and uncertainties. The sector most likely to be affected by climate change is agriculture, especially in the Mediterranean, since that sector utilizes a high proportion of the available water and land resources. At present, there is a delicate balance between water supply and demand in relation to agriculture. Climate change threatens to destabilize this.
With regard to wetlands, we still lack detailed information about the distribution, extent and use of wetlands, which makes it difficult to predict the impacts of climate change. Furthermore, changes in wetlands are normally dominated by changes in the water catchment basin. The most effective adaptations will be to minimize changes in hydrological regimes. Adaptation is no longer an option, it is becoming a necessity.
In order to cope with the impacts of climate change, and to mitigate them, a set of strategic priorities needs to be adopted:
- The first priority should be to reduce the vulnerability of wetlands and surrounding human settlements to shifts in hydro-meteorological trends, increased variability and extreme events of floods, storms, droughts, earth slides, coastal erosion, and sea level rise.
- A second priority will be to protect and restore ecosystems that provide critical resources and services to mitigate negative events.
- A third priority is to close the gap between water supply and demand in order to achieve high efficiency in water resources management.
It is unrealistic to expect adaptation will simply happen because it sounds like the right thing to do. It is necessary to involve the public in this process, to develop broad coalitions and to engage political leaders to support and communicate the adaptation process.
For downstream protected areas, delta ecosystems and coastal wetlands, the following should be undertaken:
- Inventory what there is in terms of biodiversity and wetland ecosystems, their hydrological functions and services.
- Observe climate change at local level and predict further trends and scenarios regarding possible impacts on the landscape and underlying ecosystems.
- Analyze the extent of the danger of floods, earth slides, droughts, storms and their possible damages to human and natural goods and infrastructure.
- Identify how wetland ecosystems, providing natural infrastructure, can counteract such events or mitigate their effects.
- Define spatial needs of wetland ecosystems that will fulfill such services, e.g. to prevent coastal erosion due to sea level rise, or other negative impacts.
- Plan ahead to identify compensation space for protected areas likely to be lost and sites to execute restoration and rehabilitation projects.
- Prepare local populations and stakeholders to be adaptive and to become more flexible in terms of spatial planning for protected areas and wetland ecosystem that fulfill crucial functions and provide services to humanity, as their needs are likely to evolve fast.
- Ramsar COP8 DOC.11: Climate change and wetlands: impacts, adaptation and mitigation, downloadable at www.ramsar.org/cop8_docs_index_e.htm
- Ramsar Resolution VIII.3: Climate change and wetlands: impacts, adaptation and mitigation, downloadable at www.ramsar.org/key_res_viii_index_e.htm
- Change - adaptation of water resources management to climate change, downloadable at www.waterandnature.org/change.html