Effects of climate change on terrestrial animals


has a significant direct effect on terrestrial animals, by being a major driver of the processes of speciation and extinction. The best known example of this is the Carboniferous rainforest collapse, which occurred 350 million years ago. This event decimated amphibian populations and spurred on the evolution of reptiles. In general, climate change affects animals and birdlife in various different ways. Birds lay their eggs earlier than usual in the year, plants bloom earlier and mammals come out of their hibernation state earlier.
Climate change is a natural event that has occurred throughout history. However, with the recent increased emission of CO2 in the Earth's atmosphere, abrupt climate change has occurred. It has been hypothesized that anthropogenic greenhouse gas forcing has significantly influenced global climate since about 8000 before present.
Animals have had specific responses to climate change. Species respond to climate changes by migration, adaptation, or if neither of those occur, death. These migrations can sometimes follow an animal's preferred temperature, elevation, soil, etc., as said terrain moves due to climate change. Adaptation can be either genetic or phenological, and death can occur in a local population only or as an entire species, otherwise known as extinction.
Climate changes is projected to affect individual organisms, populations, species distributions and ecosystem composition and function both directly and indirectly .
Every organism has a distinct set of preferences or requirements, a niche, and biodiversity has been tied to the diversity of animals' niches. These can include or be affected by temperature, aridity, resource availability, habitat requirements, enemies, soil characteristics, competitors, and pollinators. Since the factors that compose a niche can be so complex and interconnected, the niches of many animals are bound to be affected by climate change.
One study done by Camille Parmesan and Gary Yohe from the University of Texas at Austin shows the global fingerprint of climate change on natural systems. The results of their global analysis of 334 species were recorded to demonstrate the correlation of patterns consistent with global climate change of the 20th century. Using the IPCC's "levels of confidence", this study proved significant nonrandom behavioral changes due to global climate change with very high confidence. Furthermore, an accuracy of 74–91% change in species has displayed predicted change for species in response to climate change.

Impact of greenhouse on animals

Habitat fragmentation

During the Carboniferous rainforest collapse, the vast and lush rainforests of Euramerica were destroyed, fragmenting into small "islands" in a much less diverse landscape. This event decimated amphibian populations and spurred on the evolution of reptiles.

Increased temperatures

"Average temperature changes do not in themselves provide simple predictions about ecological consequences. Average temperatures have changed more in high latitudes than in the tropics, but tropic species are likely more sensitive to temperature changes than temperate ones".
Q10 is the rate of change of a biological or chemical system as a consequence of increasing the temperature by 10 °C.

Severe weather

With rising global temperatures, terrestrial organisms will face greater hazards in the forms of increasingly frequent and more severe meteorological conditions such as droughts, snow storms, heat waves, hurricanes, and melting glaciers and sea ice.
These harsher weather conditions will cause terrestrial wildlife many issues as their usual habitats will be significantly impacted, leading them to go extinct, migrate elsewhere or find ways to adapt to their new conditions. These ecological responses vary based on the situation. This was shown even in a 2018 study done at the University of Queensland, where over 350 observational studies were done on terrestrial animal populations, with results showing a positive correlation between increased severe weather conditions in ecosystems and population declines or extinctions.

phenology

is the study of life cycles of animals or plants due to seasonal or other variable climate changes. These responses by animals due to climate change may or may not be genetic.
Researchers are exploring ways to breed livestock like chickens, turkeys, and pigs to better withstand the heat.

Indirect effects

Effects on vegetation and agriculture

The increasing global temperature has been devastating for the polar and equatorial regions, and the change in temperature in these already extreme regions has destroyed their fragile equilibrium. In the sub-Saharan regions, deserts are experiencing severe droughts that affect both water and agricultural resources, since crop production is harshly affected.
Droughts, floods or changes in precipitation and warmth all influence the quality and amount of vegetation present in a region, in addition to the soil fertility and plant diversity. A region with vegetation or crops that have minimal tolerances and resilience to changes is at risk due to the uncertainty of the future effects of climate changes on crops and edible vegetation.
This direct effect of climate change has an indirect effect on the health of terrestrial animals, since changes in their dietary availability will impact not only herbivores but all other terrestrial creatures in their food webs. Some of the negative impacts include:
Humans may be significantly impacted as terrestrial livestock will not be immune to the ravages of climatic changes. Temperature-related illness and death can be attributed to global warming, with homeothermic animals eating less feed and exerting more energy to maintain conditions to function normally. This heat stress on terrestrial mammals can weaken their immune systems leaving them vulnerable to a multitude of associated illnesses and diseases.

Effects on the movement of disease

Changes in climate and global warming have significant influences on the biology and distribution of vector-borne diseases, parasites and their associated illnesses. Regional changes resulting from changing weather conditions and patterns within temperate climates will stimulate the reproduction of certain insect species that are vectors for disease. Therefore, tropical diseases common to certain places and affecting only certain terrestrial species may probably migrate and become endemic in many other ecosystems.

Migration

Range shifts

Range shifts are a natural response to climate change. Species with sufficient levels of mobility may respond quickly to environmental change, with species capable of undertaking long migratory movements likely to shift ranges first. Migration is not limited to animal populations—plants can migrate via passive seed dispersal, establishing new individuals where conditions allow.
"The range of plants and animals are moving in response to recent changes in climate". As temperature increases, ecosystems are particularly threatened when their niche has essentially nowhere else to move to. This hindrance is particularly prevalent in mountain ranges, for example. The speed at which climate is changing is derived from the ratio of temporal and spatial gradients of mean annual near-surface temperature.
"Mountainous biomes require the slowest velocities to keep pace with climate change. In contrast, flatter biomes, such as flooded grasslands, mangroves and deserts require much greater velocities. Overall, there is a strong correlation between topographic slope and velocity from temperature change".
Temperatures are expected to rise more than average in higher latitudes and at higher elevations. Animals living at lower elevations could migrate to higher elevations in response to climate change as temperatures rises, whereas animals in higher elevations will eventually "run out of mountain". "Results confirmed that protected large-scale elevation gradients retain diversity by allowing species to migrate in response to climate and vegetation change. The long-recognized importance of protecting landscapes has never been greater".
Over the past 40 years, species have been extending their ranges toward the poles and populations have been migrating, developing, or reproducing earlier in the spring than previously.
Similarly, dispersal and migration are crucial to preserving biodiversity as rapidly rising equatorial temperatures push an increasing number of species in poleward directions.

Adaptation

The 2007, IPCC's report stated that "adaptation will be necessary to address impacts resulting from the warming which is already unavoidable due to past emissions."
In the face of impending climate changes, humans are realizing that environmental changes are acting as stressors on terrestrial populations. When changes in climate start to exceed optimal conditions for a population, an affected species will need to respond and adapt to new conditions in order to remain competitive and thriving.

Changes in phenology

As mentioned earlier, phenology is the changing of an animal's behavior because of climatic circumstances. It may or may not be genetic. The genetic changes in animal populations have evolved adaptation to the timing of seasonal events or to season length. For example, the Canadian red squirrels are reproducing earlier in the spring, thereby capitalizing on earlier spruce cone production.
Because of the increasing evidence that humans have had a significant impact on global climate over the previous centuries, many scientists wonder how species—and the ecosystems they live in—will adapt to these changes, or if they even can.
Usually the first and most easily detectable response is a change in the species' phenotype, or its physical features. But there is a debate among scientists over whether or not these changes reflect an adaptive genetic evolution or simply phenotypic plasticity.
A recently published study by Franks et al. sought to demonstrate that a shift in the annual flowering time of the Bassica rapa plant in response to a multi-annual drought in southern California is in fact an adaptive evolutionary response. Based on the study, they concluded that post-drought genotypes appeared to be better adapted to shorter growing seasons than the pre-drought genotypes, and that this was a result of adaptive evolution.
Huntley counters the findings of Franks et al. with a study by Wu et al. that provided evidence that not only different species but also different populations of the same species exhibited markedly different potentials for the selection of heavy-metal-tolerant genotypes. This led Bradshaw and McNeilly to conclude that different populations of the same species can adapt their phenology to survive in the short term and at local sites, but genetic variation across an entire species in response to rapid climate change is not possible.
Huntley concludes that while some evolution is likely to occur in some species in relation to global climate change, it is unlikely to be sufficient to mitigate the effects of said changes, especially if they occur as rapidly as has happened in the past.
In refuting the findings of Franks et al., Huntley concludes:
"Although the demonstration of an evolutionary basis for a phenotypic response may be interesting, it is insufficient to overturn the conclusions of Bradshaw and McNeilly. Evolutionary adaptation is unlikely to be of major importance in the response of species to the climatic changes expected this century. Furthermore, even its limited potential is likely to be severely reduced as a consequence of habitat and population fragmentation, and of the rapidity and magnitude of the expected climatic changes, that together are likely to lead to rapid genetic impoverishment of many populations. A more likely outcome is that, rather as in the grasslands developed on heavy metal contaminated soils, a small number of species that happen to have the necessary genetic variance will come to dominate many plant communities, with potentially far-reaching consequences for biodiversity, ecosystem function and the ecosystem services upon which mankind depends".
There are many ways that an animal can alter its behavior, including the timing of its reproduction, mating, and migration.

Evolutionary

Adaptive shifts in the timing of seasonal events should precede adaptive shifts of thermal optima or increased heat tolerance over evolutionary time, and that is the pattern that is emerging.
It has been hypothesized that as temperature increases, body size would decrease. Smaller body size would dissipate heat more efficiently, so in an increased temperature environment one would expect an animal to be smaller. The opposite also holds true: when temperature decreases, studies have shown with great correlation that body size increases.
Climate change has been associated with changes in plant size as well as animal size.

Factors contributing to adaptation

Short generational times improve adaptability; e.g., many microbial disease organisms, small insects, common fishery species and annual plants are thought to be more highly adaptive.
Wide dispersal areas allow animals to migrate and move to an environment better suitable in an effort to handle climate change.
Broad climatic tolerance is the ability of an animal to withstand a large range of conditions. For example, the kangaroo has a very broad climatic tolerance.
Generalists are non-habitat species in that they are not restricted to a very specific location, environment, food source, etc. The American coyote is an example of a generalist.
Opportunistic species feed and adapt to many changes.

Factors hindering adaptation

Long generation times limit the rate at which a species can become more varied.
Poorly dispersed animals are unable to migrate to escape and survive the climate change.
Narrow climatic tolerance in animals inhibits their adaptability, because their basic survival needs cannot range in location, temperature or resources.
A population confined to one geographic location, such as a population that lives in cold regions at the tops of low-lying mountains, does not have a simple option of migration. These animals are in habitats that will run out as climate change increases and global warming becomes more impactful.

Extinction or extirpation

According to Stuart L. Pimm and his coauthors, human actions have raised species' extinction or extirpation rates to three orders of magnitude above their natural background rates. Pimm says, " predict that 400 to 500 of the world's 8500 landbird species will go extinct by 2100 with a warming estimate of 2.8 degrees Celsius. A further 2150 species will be at risk of extinction".
In Australia, the grey-headed robin is restricted to rainforests of the wet tropics region and another population in the New Guinea highlands. Although in some places it can be locally common, this bird's range is very restricted; it is found only in the northeast of Queensland, and there only in the higher-altitude rainforest. This is a projection of its range as climate change continues. This animal could be considered in danger of extinction.
A similar but more dramatic prediction is cast for the lemuroid ringtail possum. With a high enough temperature shift, this animal will become extinct.
Global warming as caused by humans is confirmed by the IPCC fourth assessment to be "very likely". This being the case, a tipping point may be reached for many species, leading ultimately to extinction.
Sometimes a species may react in one of the other two ways, by moving or by adapting, and yet find that its efforts do not save it from extinction. While not yet extinct, the European pied flycatcher, a small insectivorous bird that migrates to western Europe from Africa each spring, has declined to 10% of its former population. This has occurred at the same time as a main food source for the young flycatchers, caterpillars, have begun to peak much earlier. Although the birds have also begun to arrive earlier, they have not yet caught up to the peaking of the caterpillars. This individual species may or may not go extinct, but it demonstrates that a species can sometimes begin to move or adapt and yet find itself dying nevertheless.