Observations and Impacts of Rapid Climate Change in New Zealand

Transcription

1 Cameron and Kim - New Zealand Climate Change 28 Observations and Impacts of Rapid Climate Change in New Zealand Jillian Cameron and Ji Young Kim Understanding global climate change is a complicated task involving several unpredictable and hard to measure variables. In this paper, we have chosen to discuss observable climate change, such as flood levels, plant distribution and glacial effects in a single place, New Zealand. After defining climate change, we viewed the data gathered on climate variability in New Zealand as a model for the possible climate changes on a global level to gain a better understanding of the inevitable change in climate that occurs through natural means. We discovered that through these studies that rapid climate change is not only possible but also occurring in New Zealand presently. Rapid climate change has also increased in speed due to the human interaction with the planet. By analyzing these studies, we will gain further knowledge of the ever-changing global climate and may help to manipulate the climate change to help the various land systems. Introduction According to the belief of many scientists through much of the 20 th century, the great climate changes were seen to only occur over several thousands of years (Weart, 2003). It was difficult to imagine that climate change could occur over such a short time span of only a few hundred years or even decades. However, with new evidence of oxygen isotopes found in Greenland ice cores and the observable changes brought on by the greenhouse effect and global warming, the conventional belief that climate change occurs only over thousands of years has been refuted. Now, scientists have more plentiful evidence to support the fact that rapid climate change can occur. Today, scientists acknowledge that natural climate change can happen over the span of a single decade. However, this rate of change has also been increased by human abuse of the environment (Weart, 2003). In order to exam in the issue of rapid climate change, this paper will look at the change in climate through various methods. We will refer to a study that examine the pollen distribution in three different areas of New Zealand in order to understand various temperature changes and glacial impact, flood level changes in both the North Island and South Island of New Zealand. We will also focus on the increase and decrease in precipitation over a period of time. Also, we have compared several studies concerning the natural causes and the effect of these climate changes on New Zealand land systems. By connecting these different studies, we will form a more complete picture of the many causes of rapid climate change. Global Climate Change Global climate change is an important phenomenon of the earth process. Global climate change is significant. It affects the sea level, the distribution of climactic belts and thus, the habitats, agriculture lands, and landscapes (Marshak, 2001). Climate change is a process, which through a chain of events eventually causes large impacts on the earth system. For example, a rise in the average global temperatures of only a few degrees could potentially bring about conditions that could melt enough polar ice sheets to cause a rise in sea level that could turn into a flood on coastal population centers. Global climate change occurs in two types: long term climate change and short-term climate change. Long term climate change takes place over millions of years while short-term climate change takes place over mere decades. This distinction is particularly important in explaining the causes of short-term change. Short-term climate effects are hypothesized to occur as a result of fluctuations in the solar radiation, changes in the earth tilt and orbit, changes in the reflectivity of the earth, or changes in ocean currents (Marshak, 2001). Long-term climate effects occur over millions and millions of years as a result of accumulated greenhouse and icehouse effects (Marshak, 2001). Geologists and climatologists can study the climate changes by two approaches. One

2 Cameron and Kim - New Zealand Climate Change 29 is by measuring past climate changes to document the magnitude and the rate at which the change occurred (Marshak, 2001). The other measure is to make computer program to calculate factors of the earth processes, such as atmospheric composition, topography of the ocean currents, and the earth orbit, that affect the climate, to predict future climate patterns and further understand what effects climate change(marshak, 2001). The greenhouse gases, such as carbon dioxide and methane, are also seen to affect the climate. For example, an increase in carbon dioxide concentration warms the climate while a decrease will cool the climate (Marshak, 2001). Human activities that involve emitting carbon dioxide and other gases, such as the ever-increasing use of cars, factories, and coal, which are a big culprit in the rise of greenhouse gases in the air and in turn accelerate the rate of climate changing into a warmer environment. Rapid Climate Change Observed in New Zealand New Zealand is a particularly good place to study climate change,... because of its location within the Southern Oceans mid-latitudes close to the zone of southern westerlies. Furthermore, it is located in close proximity to the oceanic sub-tropic convergence zone [which] makes it sensitive to change in atmospheric and oceanic circulation (Vandergoes and Fitzsimons, 2003). Thus, New Zealand is a prime location because it encompasses a multitude of factors that can be applied to many other locations around the globe. However, along with its location, New Zealand also was home to glaciers, which help scientists study climate change because of the deposits left by the last ice age. Therefore, New Zealand provides ample information for understanding climate changes concerning glaciers as well as more modernly, how humans have effected and increased the frequency of certain climate change. (Vandergoes and Fitzsimons, 2003). Many studies have been conducted not only testing different natural occurrences to gage climate change but also using a variety of mediums to discern the viability of climate change and its affects. A recent study of New Zealand climate trends and variability provides supportive evidence for the concept of rapid climate change. Trends in the mean, maximum and minimum air temperatures, sunshine and cloud cover in the South Pacific from 1951 to 1991 have been examined using data from stations from the South Pacific Historical Climate Data Network (Salinger, 1996). Detailed analysis for New Zealand consisted of 20 sites and an anomaly series from each site, which was combined to form a single time series of mean annual climate anomalies for each region (Salinger, 1996). The mean air temperature has increased by 0.12 Celsius in the New Zealand region, minima increase at almost twice the rate of maxima (0.15 cf 0.08 Celsius per decade) with a subsequent decrease in the difference between maximum and minimum temperatures (DTR) (Salinger, 1996). DTR is an important measure because it is used in observing warming by changes in daily minimum (night time) air temperature with daily maximums (daytime) air temperatures (Salinger, 1996). Sunshine has also decreased (0.6% per decade) as well as the cloud cover (Salinger, 1996). On the whole, DTR in this region increases and cloud cover decreased significantly. Another study by Marcus Vandergoes and Sean Fitzsimons examines the different types of pollen and subsequent foliage found in three different sites around New Zealand. Understanding the types, frequency and age of plant life in a specific area can help scientists ascertain shifts in climate patterns because certain plants are more likely to grow in certain climates. This study also mentions the shift in relation to the Last Glacial-Interglacial Transition in an effort to further connect the shifts in climate with the deglacialization of the earth and more specifically New Zealand. Both the pollen study and other studies done concerning deglacialization have placed the climate changes in the same period of time, thereby increasing the legitimacy of their findings. As the temperature and precipitation increased due to the deglacialization, certain types of pollen began to become more prevalent and spread to create shrubs and plant life (Vandergoes & Fitzsimons, 2003). Since deglacialization is not a very rapid process in terms of the life span of the average plant, the plants that grew during the deglacialization period were plants that do not require very high temperatures or heavy rainfall (Vandergoes & Fitzsimons, 2003). These plants were found to be the oldest in the area and therefore

3 Cameron and Kim - New Zealand Climate Change 30 confirm the deglacialization timing. As New Zealand became increasingly warmer, the abundance of the cooler climate plants began to decrease and warmer weather plants became more widespread (Vandergoes & Fitzsimons, 2003). There was an increase in precipitation, which also affected the type of plants and foliage that grew in these areas (Vandergoes & Fitzsimons, 2003). Therefore this study concludes that there were two distinct patterns of climate change: the stages of warming that caused certain plants to increase and decrease in distribution and growth and the affects of the increased rainfall, which resulted in a generally wetter environment, causing those earlier plants which thrived in dryer climates to decrease in abundance and plants which thrive in the newly wetter environment increase in abundance. These studies show that the movement and understanding of glaciers is helpful and necessary in the understanding of climate change (Vandergoes & Fitzsimons, 2003). The study of the increase and decrease of water flow and levels is very important when trying to understand climate change. A study by A.I McKerchar and R.D. Henderson of the National Institute of Water and Atmospheric Research in New Zealand compared flooding on the North Island and to the South Island of New Zealand. It measured water levels from 1978 to 1999 and concluded that the water levels were decreasing in the North Island and increasing in the South Islands (McKerchar & Henderson, 2003). There were more severe floods in the south and less severe floods in the north. Although measuring water can prove to be very inaccurate as well as inconsistent, the data gathered was consistent enough to conclude that the flood levels on the North Island increased by 5% while the rainfall levels in the South Island increased by 8% (McKerchar & Henderson, 2003). The study concludes maintaining that the process of climate change is a step process: change with plateaus of consistency (McKerchar & Henderson, 2003). The climate phenomena of El Nino and La Nina are also said to have affected the rainfall distribution in the areas (McKerchar & Henderson, 2003). Thus, the climate of the area affected the flood levels. These two studies tested two very different qualities of New Zealand to further the understanding and explain climate change as a model for the rest of the world. Also, they show how those factors are all absolutely interconnected and yet can affect different components of climate change. Climate Change Effects on Land Systems and Soils Climate change directly affects the soil and land systems. About 65% percent of New Zealand economy is based on its natural and managed land systems and soils. New Zealand climatic modeling suggests that increases in global average surface temperatures of between 2 and 4.5 Celsius may occur by the end of the next century (Tate, 1996). By keeping track of the climate changes and its effect on the soil, humans can better maintain their natural environment. The information found regarding how to deal and best cope with changes of land system soil would allow for more efficient exploitation of the positive effects and help offset negative effects of climate change. New Zealand land composition is based largely on grasslands and forests. Land use has caused deforestation of two thirds of the original forests for use as grasslands. New Zealand grasslands thrive in a wide range of climatic and soil environments (Tate, 1996). Most of the combined effects of climate warming and carbon dioxide fertilization would be positive for the soil in the grasslands because more could grow over a longer period of time, due to lengthier periods of warmer temperatures (Tate, 1996). Since climate warming and carbon dioxide fertilization is beneficial to grasslands, environmental policies do not need to be set to take advantage of the positive externality of the global warming. Warming can be allowed to continue, however, things that might result in a rapid climate cooling effect should be avoided to help the warming continue. Forests have a different reaction to climate change. Since forest plants have adapted to welldefined temperature regimes, climate change will result in different responses between individual species and a change in forest composition (Tate, 1996). Most of New Zealand planted forests grow within a mean annual temperature range of degrees Celsius (Tate, 1996). However, climate change that causes disequilibrium in the forest patterns can result a reduction in forest productivity

4 Cameron and Kim - New Zealand Climate Change 31 and health, isolation of seed sources, and an increased threat to the survival of native habitants (Tate, 1996). Furthermore, it may increase the risk of damage caused by the spread of diseases and the warmer temperatures may raise the risks of fire in the forests (Tate, 1996). The effects of elevated carbon dioxide on forests also vary by the types of forest. The effects on mature forests are insignificant because they do not make up a large portion of the forest land, however in the eastern parts of the island where the soil water deficient more extreme the physiological response are stronger, thus, more significant (Tate, 1996). Since the effect of climate change is varied, the prescribed response to natural forests would be just as varied. Global warming due to the greenhouse effect has a negative affect on the natural forests of New Zealand because of the rise in temperature. Also, policies should attempt to moderate the increased level of carbon dioxide produced in New Zealand because it would affect water deficient forests significantly. Human activities in the past hundred years have increase the greenhouse effect by increasing the amount of carbon dioxide in the atmosphere through the increased use of cars and the increased burning of coal. Therefore, policies geared toward changing the behavior of human to decrease the level of carbon dioxide would help prevent the temperature from steadily rising. Another important land system in New Zealand is the croplands. Soil samples of the croplands revealed that an increased amount of carbon dioxide fertilization could greatly reduce the natural decline of nutrients in the soil (Tate, 1996). In this case, a warmer climate can produce very beneficial results. Even in nutrient rich ecosystems, unlimited by water, carbon dioxide induced increases in a net primary production may not necessarily be reflected in an increase in plant and crop growth (Tate, 1996). Reduction in soil organic matter causes loss of favorable soil structure and water holding capacity (Tate, 1996). This point stresses the fact that water is an important factor in the soil. Thus, we can infer that a climate change that includes a moderate increase in precipitation is further beneficial to the soil of the cropland system. Therefore, policies for croplands should be directed to keep warming at a stable rate in order to avoid rapid increase or rapid decrease in temperature. Conclusion Since the study of climate change began, scientists have come a long way in their understanding of rapid climate change. New Zealand has and will continue to provide ample evidence for scientists to study not only the causes of rapid climate change. Rapid climate change is brought on by a number of factors and manifests itself through increased sea levels, increased precipitation, increasing and decreasing flood levels as well as the distribution of plant life, to name a few. By combining the findings of several studies in this paper, a broader understanding of climate change on a number of levels is achieved, such as predicting future changes, and manipulating those changes. Although the collective population of the world is not yet ready to admit and take responsibility for our harmful effects on the world environment, there have been several policies created in New Zealand in an attempt to slow down the human effect on climate change. These policies were created from a purely economic standpoint because climate change often affects the agricultural community more heavily than other industries. Environmental scientists are also looking for ways to lessen the impact of humans on the climate. Rapid climate changes should not be overlooked because there is so much documentation that shows that climate change is occurring more rapidly and it is directly related to the on the negative effects that humans have on the environment. Ironically, the change in climate that is increasingly caused by human beings affects our day-to-day lives in a very direct way and the environment we live in. Climate change affects every component of the earth in a profound way and therefore should and will continue to be studied in order to recognize and predict its full effects.

5 Cameron and Kim - New Zealand Climate Change 32 References Marshak, S., Earth, Portrait of a Planet., New York: W.W. Norton & Company, , McKerchar, A., Henderson, R., Shifts in flood and low-flood regimes in New Zealand due to Interdecadal Climate Variations, Hydrological Science Journal, 48, , Salinger, M. J., Observed Variability and change in climate and sea level in Australia, New Zealand, and the South Pacific., National Institute of Water and Atmospheric Research, , Tate, K.R.,. Impacts of Climate Change on Soils and Land Systems in New Zealand, Land Care Research New Zealand, , Vandergoes, M., Fitzsimons, S., The Last Glacial-Interglacial Transition in South Westland, New Zealand, paleoecological insight into midlatitude Southern Hemisphere Climate Change, Quaternary Science Reviews, 22, , Weart, S., The Discovery of Rapid Climate Change. Physics Today. American Institute of Physics, 30-36, August 2003.