THE EFFECTS OF CLIMATE CHANGE ON ECOSYSTEMS By Mwape Daka

Visible effects of climate change

Climate change is a significant and lasting change in the statistical distribution of weather patterns over a long period of time (Ranging from decades to millions of years), it is a long-term shift in the weather conditions identified in changes in temperature, precipitation, winds and other indicators. Climate change can involve both changes in average conditions and changes in variability. It may be a change in average weather conditions, or in distribution of weather around the average conditions.

Climate change is caused by factors such as biotic processes, variations in solar radiations received by earth and volcanic eruptions. Certain human activities have also been identified as significant causes of recent climate change often referred to as global warming.

The Earth naturally has variable climatic conditions on all time scales. The Earth’s energy balance is determined by the balance between the incoming and outgoing energy, this energy regulates the long and short-term climatic state and average temperature conditions.

Any factor that causes a sustained change to the amount of incoming energy or amount of outgoing energy can lead to climate change.

These factors are external to the climate system and are therefore, called “climate forcers”, giving the idea that they force or push the climate towards a new and long-term state, either cooler or warmer depending on the cause of change.

Factors Affecting Climate Change

Factors that cause climate change can be divided into two categories-those related to natural processes and those related to human activities.

Natural causes include factors which are external to the climate system, such as changes in volcanic activity, solar output and the Earth’s orbit around the sun. Whereas human causes include the burning of fossil fuels and the conversion of land for forestry and agriculture.

There is a growing consensus that human activities have induced dramatic and unprecedented changes in the global chemical and physical environment, including an increase in atmospheric carbon dioxide concentrations, an increase in mean annual temperature and changes in timing and magnitude of precipitation.

Current predictions give an indication that there is a high chance of atmospheric carbon dioxide concentrations doubling during the present century, unless greenhouse gas emissions are significantly curtailed. If this happens; there will be an additional increase in mean global temperature, alterations in patterns of global air circulation and hydrologic cycling that will affect global and regional precipitation patterns, and increase the frequency and magnitude of severe weather events, including droughts and floods (Easterling et al., 2000). Consequently, the climatic and environmental conditions for the terrestrial ecosystems in the future include increased atmospheric carbon dioxide, increased temperature, changes in precipitation patterns and increased frequencies of extreme climatic events.

These changes in atmospheric composition are likely to affect the earth’s terrestrial (living or growing on land rather than the water or air) and Aquatic (Living or growing in water) ecosystems directly, through for example, increased carbon sequestration by photosynthesizing organisms in an atmosphere richer in carbon dioxide. Water availability and temperature are fundamental drivers of all chemical and biological processes, they therefore play central roles in determining the future structure and functioning of the terrestrial ecosystems.

The magnitude of projected climate changes would render ecosystems vulnerable to biome shifts, phenology changes, wildfire increases, species extinctions, and other impacts.

EFFECTS OF CLIMATE CHANGE

Effects on aquatic ecosystems

Water temperatures of most running water ecosystems are expected to rise due to Global warming, Global warming is expected to increase water temperatures (Allan et al. 2005).

Typically, solar radiation is the greatest source of heat in freshwater, this is particularly true for rivers or streams that are exposed to direct sunlight over most of their surface.

In water bodies; climate change affects the following:

Turbidity

Turbidity is likely to be more critical in streams and rivers than in lakes because water levels can change rapidly in streams and rivers.  When climates are warmer; streams and rivers may be subjected to:

• Increased erosion: Comes as a result of increased flow associated with extreme weather events.
• Enhanced permafrost thawing (or the defrosting of permanently frozen land): This thawing may increase sediment and organic matter loads in Far North streams and rivers, which may in turn reduce light penetration and productivity.

Biological Diversity

There variety of species living in a stream or river can vary from the headwaters to the outlet, and can be influenced by the flow, temperature, substrate, and nutrients available along the stream.

Some of the affected biodiversity

Warmer climate

• Reduces habitat availability: Warmer air temperatures and warming of surface waters causes the cold water stream habitat for some fish species to decrease.
• Increase stress on biota: Streams and river biota undergoes high levels of thermal stress as a result of warming. Rivers with low oxygen at low flows will severely limit biota survival and activity (Reiger et al. 1996).

 Climate change is projected to cause significant alterations to aquatic bio-geochemical processes, (including carbon dynamics), aquatic food web structure, dynamics and biodiversity, primary and secondary production; and, affect the range, distribution and habitat quality/quantity of aquatic mammals and waterfowl. Projected enhanced permafrost thawing is very likely to increase nutrient, sediment, and carbon loadings to aquatic systems, resulting in both positive and negative effects on freshwater chemistry. Nutrient and carbon enrichment will enhance nutrient cycling and productivity, and alter the generation and consumption of carbon-based trace gases. Consequently, the status of aquatic ecosystems as carbon sinks or sources is very likely to change.

Climate change will also very likely affect the biodiversity of freshwater ecosystems across most of the Arctic. The magnitude, extent, and duration of the impacts and responses will be system and location-dependent. Projected effects on aquatic mammals and waterfowl include altered migration routes and timing; a possible increase in the incidence of mortality and decreased growth and productivity from disease and/or parasites; and, probable changes in habitat suitability and timing of availability.

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