Words Bassam Alkantar

Climate-warming temperatures might be expected to affect the sex ratio of species if sex determination is temperature-dependent. Several studies show that indirect climate effects could also change sex ratios in species in which sex is genetically determined, and also damage reproductive fitness. Over four decades, sex ratios in populations of a dioecious alpine plant have shifted toward females as a result of the different water needs of the male and female plants. The lack of males has reduced the reproductive success and fitness of the females. Similar subtle differences between sexes with regard to environmental sensitivities could eventually lead to population declines. Humans are also seeing the effects of climate change on their sex drive. According to a study, the climate change that is causing more scorching hot days could be bringing down the birth rate in many countries.

Hot weather is killing our sex drive

Researchers used historical, vital statistics and other sources to look at the number of babies born about nine months after really hot days, which they defined as above 27 degrees, based on National Climate Center Data from weather stations across the United States. The researchers found that, for every day that soared above 27 degrees — and in many cases above 32 degrees — between 1931 and 2010, there were 0.4 percent fewer births nine months later. The impact of one of these scorching days was that around 1,165 fewer babies were born in the United States.

Over a longer period, this could mean around 100,000 fewer births in the United States every year, based on climate change models that predict that the number of these really hot days will increase from the current number of around 30 a year to around 90.


Temperature-dependent sex determination (TSD)

Some reptiles, such as crocodilians and some turtles, are known to display temperature-dependent sex determination (TSD), whereby the ambient temperature of the developing eggs determines the hatchling’s sex. According to the study provided by the National Institutes of Natural Sciences, for the American alligator’s eggs, incubation at 33 ºC produces mostly males, while incubation at 30 ºC produces mostly females. An international joint research team, consisting of members from Japan and members from the U.S., has determined that the thermosensor protein TRPV4 is associated with TSD in the American alligator. The research has been published in Scientific Reports. This is the first demonstrated report of a biomolecule associated with regulation of the very unique temperature-dependent sex determination mechanism.

Climate change’s effect on valerian plant

For the valerian plant, the higher elevations in the Colorado Rocky Mountains are becoming much more co-ed. And the primary reason appears to be climate change. In a study appearing in Science, University of California environmental biologists report that a changing climate over the past four decades has significantly changed the growth patterns of male and female Valeriana edulis. Their work is the first to fully explain sex-specific species’ responses to climate change.

The Valerian plant is dioecious, meaning that individual plants are either male or female. Unlike the majority of flowering plants, these plants cannot self-fertilize. Other well-known dioecious species include asparagus, ginko, papaya, holly, spinach, pistachio, willow, and aspen. In the Colorado Rockies, the sex ratio of the valerian populations traditionally changed with climate from low elevation (50 percent male), where it’s hot and dry, to high elevation (only 20 percent male), where it’s cool and wet. At the highest elevations, the rarity of pollen-releasing males reduces the number of seeds produced by female plants.


Reproduction patterns of sea turtles

Researchers from Florida Atlantic University have published the results of a four-year study on the effects of turtle nest temperatures and sand temperatures and on the sex of hatchlings in the journal Endangered Species Research. Marine turtles deposit their eggs in underground nests where they develop unattended and without parental care. Incubation temperature varies with environmental conditions, including rainfall, sun, shade, and sand type, and affects developmental rates, hatching and emergence success, and the sex of embryos.

Although the loggerhead turtle has been around for more than 60 million years, drought, heavy rainfalls, and climatic changes are impacting hatchling sex ratios and influencing future reproduction. Because sea turtles don’t have an X or Y chromosome, their sex is defined during development by the incubation environment. Warmer conditions produce females and cooler conditions produce males.

Reef fish can adjust sex ratios as oceans warm

Using a multigenerational experiment, research at the University of Technology Sydney has shown for the first time that when reef fish parents develop from early life at elevated temperatures, they can adjust their offspring’s sex through non-genetic and non-behavioral means. The study, published in Global Change Biology, demonstrates that the mechanisms involved in restoring offspring sex ratios across generations are switched on during early development of the parents and do not simply occur as a result of adults being exposed to higher temperatures.

The ability to compensate for the sex bias caused by rising temperatures is an important trait that could help to limit the impacts of ocean warming on reef fish populations and other species. However the research also suggests that when developmental temperature is too hot, there is a limit to this “transgenerational plasticity.”

Increasingly erratic rainfall patterns

The humidity of the south of the USA creates a climate conducive to amphibians. In the Southeast, more than 140 species of frogs, toads and salamanders make this a biodiversity hotspot. At night the ponds and swamps emit the sound of their symphonic noises, and it’s something that the U.S. Geological Survey’s Amphibian Research and Monitoring Initiative, or ARMI, is monitoring closely.

According to a study provided by the United States Geological Survey, climate change projections indicate that rainfall will increasingly come in pulses, with more flooding and longer periods of drought. Scientists have long suspected that climate change is an important factor in amphibian declines, and resource managers are asking whether conservation measures might help species to persist or adapt in a changing climate.

Shrinking goats

Alpine goats appear to be shrinking in size as they react to changes in climate, according to new research from Durham University. The researchers studied the impact of changes in temperature on the body size of Alpine chamois, a species of mountain goat, over the past 30 years. To their surprise, they discovered that young chamois now weigh about 25 per cent less than animals of the same age in the 1980s. In recent years, decreases in body size have been identified in a variety of animal species, and have frequently been linked to the changing climate. However, the researchers say that the decline in size of chamois observed in this study is striking in its speed and magnitude. The research, funded by the Natural Environment Research Council, was published in the journal Frontiers in Zoology.

The team delved into long-term records of chamois body weights provided by hunters in the Italian Alps. They discovered that the declines were closely linked to the warming climate in the region that was studied, which became 3-4 degrees Centigrade warmer during the 30 years of the study.

To date, most studies have found that animals are becoming smaller because the changing climate is reducing the availability or nutritional content of their food. However, this study found no evidence that the productivity of Alpine meadows grazed by chamois had been affected by the warming climate. Instead, the team believes that higher temperatures are affecting how chamois behave.