Climate Change Poses Challenges to Wildlife

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Recent years have seen some of the warmest global surface temperatures on record. However the temperature increase in some parts of the world (in red) has been higher than the long-term average, while other areas (blue) have seen less of an increase. Image by NOAA

There is strengthening evidence that the world is warming. As well as the impacts on human society (from storms, drought, sea-level rise, disease, etc.), science also predict that this will affect the natural world in various ways.

Scientists have been recently looking into this aspect, including some studies that rely upon citizen science.

Species Movement: Alien Invasions

As local temperatures increase, there are opportunities for species to colonize new areas. This has already been seen in the United Kingdom, where the Breeding Bird Survey (BBS) has noted an increase in the number of species recorded over a 12 year period of rising temperatures.

This could be considered as good news, but the increase occurs mostly among the more adaptable species.

On the other hand, those who require more specialized conditions (such as in natural grassland and upland areas) are going into decline. Similarly, an increase in the number of warm-climate bird species was detected in the Czech Republic during the 1980’s, but again with loss of specialization.

Meanwhile, over a 44-year period (during which average annual temperatures rose by 1.3oC), North American BBS data showed that many US bird species had shifted northward in their range. Scientists have suggested that temperature increases in winter and spring were a driving force behind this movement, which was particularly noticed among those species that over-winter in the North-East United States.

Many birds are able to respond to climate change by relocating to new areas, but what of plants and insects? In the Swiss mountains, rather than expanding northward, some flowers and butterflies are now being found at higher altitudes, and the tree line has also risen.

New insect species are also being seen in Switzerland, though some are becoming invasive as they out-compete the natives. In the UK, the Brown Argus butterfly is spreading northward in response to climate warming. While doing so they have adapted to a new food plant, though experiments have also shown that they cannot so easily switch back again. This is seen as further evidence that climate change can result in a loss of adaptability.

Summer Travelers

Climate models predict that the greatest temperature changes will occur at high latitudes (i.e.: nearer the poles than the Equator).  There is evidence that migrating birds are arriving earlier to start breeding in these areas, though their migration routes can be disrupted if traditional stopover points are affected by warming (for example, with wetlands drying up). Long-distance migrants could be particularly affected by increased desertification along their routes.

Even when they arrive, they may find that conditions have become more challenging. In Eastern England, changes in rainfall patterns (another consequence of climate change) are leading to increased winter floods. Waterlogged nests and a reduction in insect availability during flood conditions  have adversely affected the breeding results for migrant warblers.

In Switzerland, warmer spring temperatures are resulting in earlier flowering times. Image by U.S. Library of Congress.

The Early Bird?

With documented records going back over 300 years, phenology is a long-established form of citizen science, which records the timing of seasonal events, such as:

  • The first leaf appearance on oak trees
  • The first spring arrival (and latest departure in fall) of migrant swallows
  • The earliest sighting of emerging bumblebees

Using these observations, it’s been possible to identify where climate change might be responsible for alterations in the timing of such events. For example: in Switzerland, plants are flowering earlier in recent warmer springs, and butterflies are emerging earlier. Amphibians are also starting to breed earlier, though increases in summer droughts may threaten their ponds.

Not all animals are responding to warmer springs, and this can also cause problems. For instance: European Roe Deer are failing to adapt their birth times in response to earlier spring growth among plants. By the time that they do produce their young, the more easily digestible early foliage is beginning to toughen. As a result, Roe Deer are not breeding as successfully as they have in the past.

Biodiversity and Climate Change: Looking to the Future

In addition to recording what has already taken place, some scientists are looking at how continuing climate change might affect biodiversity in the future. In Colombia, a review of species distribution and climate models predicts that most native bird species there will suffer reductions in range of between 33 and 43%, as well as fragmentation of the remaining populations. In the worst case scenario, up to 12% of the species studied could become extinct.

Before the introduction of weather forecasts on TV and radio, many people around the world used to monitor the progress of the seasons by studying the natural world. This is now becoming an important method for observing climate change in action.

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