Phenological changes and mankind

This post will look at some of the impacts phenological changes can have on mankind, and whether these are good or bad.

"Ecosystem services" are the benefits people gain from ecosystems. They can be split up into into provisioning, regulating, cultural and supporting services (Fig. 1).

Fig. 1 Examples of ecosystem services by type. Taken from unep.org.

Provisioning services

Pelagic plankton and fish in the North Sea show phenological changes in response to warming sea surface temperatures, but their responses are mismatched in time (Edwards and Richardson, 2004). We've heard about decoupling between trophic levels before. In this context, these phenological mismatches could detrimentally effect fisheries, because the success of fish depends on their synchronisation with growth of plankton (because they eat them).

Regulating services

We've heard before that the growing season is lengthening. A longer growing season in northern Europe (Fig. 2) could be beneficial for agricultural yields and insect populations, and allow us to introduce crops to new areas where they previously could not grow (LaValle et al., 2009).

 

Fig. 2. Rate of change of crop growing season 1975-2007. Taken from LaValle et al. (2009).

However, again, there is concern that there could be mismatches in the phenology of flower production and pollinator flight activity. Memmott et al. (2007) used phenological data from 1884 - 1916 on the first and last dates of flowering, and visits from pollinators, to predict what would happen to plant-pollinator interactions in a simulation of future global warming for the years 2070-2100. They found that most pollinators would be at risk in this scenario, and that local extinction of pollinators will put plant sexual reproduction at risk, and cause plant populations to decline.

Cultural services

Ecotourism has explicit links with plant phenology:

"...autumn tourists, including “leaf peepers”, are estimated to spend US$375 m in Vermont alone ... In Japan, both autumn colour watching (“momijigari”) and viewing of spring flowers (“hanami”) are hugely important; 10 million visitors a year visit the famous 59-ha Arashiyama National Forest near Kyoto ... and when cherry flowering coincides with public holidays this attracts an additional 1.4 million tourists to Hirosaki... Cherry flowering is also a huge attraction in Korea, China and across North America where an estimated 700,000 visitors visit Washington D.C. for the cherry blossom festival..." - Sparks et al. (2012; p. 1)

Sparks et al. (2012) looked at the spring snowflake (Leucojum vernum) (Fig. 3) which the flowering of is a tourist attraction in Poland. They found that earlier flowering was associated with a long flower duration. This would be beneficial for ecotourism.

Fig. 3. Spring snowflake blossom heralds the start of spring. Source: http://www.panoramio.com/photo/68598215

This is all well and good. But ecosystem services frame the biosphere as valuable only because it provides mankind with something, rather than respecting life for its intrinsic value.

Delayed autumn senescence

from https://www.flickr.com/photos/andrewsteele/4082262513https://www.flickr.com/photos/andrewsteele/4082262513

The growing season at mid-to-high latitudes has been lengthening as a result of climate change. This is primarily due to an advancement of spring, but it's also partly due to a delay in autumn phenologies (IPCC, 2007). Indeed, we're having quite a mild autumn this year, and it seems natural to conclude that this would cause leaves to retain their leaves for longer, and to change colour later. However, changes in autumn phenologies are less well understood than spring ones. I touched on this in my previous post. Advancing spring phenologies correlate well with rising temperatures, but delayed autumn phenologies correlate less well, which implies that there are other factors playing a role.

Similarly to some instances of bird migration and mammal hibernation, in many trees, growth cessation, the first stage in winter dormancy, is initiated by day length (Wareing, 1956). It was thought that Populus' autumn phenologies are controlled by photoperiod. But Taylor et al. (2007) performed an experiment where Populus trees were grown with elevated CO2 (550ppm, we're now at ~400ppm) and found that this delays autumn leaf colour changes and leaf fall. Rhode at al. (2011) found that Populus trees also found that temperature had an effect. However, these studies are all done on one species and it's fairly certain that there will be species-specific responses to the same environmental changes.

Mammals

Studies of changes in phenology in response to climate change have focused particularly on migratory birds, since they may be more likely to experience mismatches between their time of arrival and the coming of spring in their breeding grounds (see previous post). What about mammals? Let's have a look at a couple of studies.

Hibernation. Like migratory birds’ migrations, hibernation is controlled by “endogenous rhythms” – i.e. an innate response to day length. However, mammals are able to alter the phenology of their hibernation in response to climate change, through “phenotypic plasticity” - i.e. one genotype can produce different phenotypes depending on environmental conditions.  Over longer timescales, it’s likely that microevolution of phenological traits will be more important for species to survive. 

Reproduction. Chillingham cattle are a rare breed of cattle. A wild population roams in Northumberland and there are records of their births and deaths since the 1860s. This breed gives birth throughout the year, but it’s been found that they’ve been having more calves during the winter. Weather data points to warmer springs as the reason: the cattle have a 9 month gestation period, and have been conceiving earlier because of an earlier availability of vegetation for food. This is bad news, because winter born calves don’t do as well.

Stay posted for more fascinating phenological facts ;)

Birds of Britain...