Changes in the phenology of many plants, mainly deciduous trees, can be used as bio-indicator. As a response to global warming, nowadays many phenological stages are observed earlier in the spring and the length of the vegetation period is increasing in most temperate or mountain regions.
As suggested by Stefan Siebert , Phenological study (i.e. the temporal study of different life cycle events of a plant) is good bio indicator of the climate change.
Some important references are,
Corlett, R.T., Lafrankie, J.V. 1998. Potential impacts of climate change on tropical Asian forests through an influence on phenology. Climate Change, 39: 439-453.
Karmer, K. 1997. Phenology and growth of European trees in relation to climate change. pp. 39-50. In: H. Leith & M.D. Schwartz (ed.) Phenology of Seasonal Climates I. Bakhuys, The Netherlands.
Mezel, A. 2002. Phenology: Its importance to the global change community. An editorial comment. Climate Change. 54: 379-385.
Kushwaha, C.P. & Singh, K.P., 2008. India needs phenological stations network. Current Science 95(7): 832-834.
In the oceans some species are well adapted to certain environmental regimes. As oceans are well connected the biogeography can change, which is often correlated (i.e. linked) to climate change indicators (like temperature). One group of such species are copepods.
Notable studies are published by Gregory Beaugrand, one of which is:
Beaugrand, Luczak and Edwards, 2009. Global Change Biology 15. doi: 10.1111/j.1365-2486.2009.01848.x
I may also recommend:
Barton et al., 2013. The biogeography of marine plankton traits. Ecology Letters. doi: 10.1111/ele.12063
Ji et al., 2010. Marine plankton phenology and life history in a changing climate. J Plankton Research 32(10). DOI: 10.1093/plankt/fbq062 and
Stegert, Ji and Davis. 2010. Influence of projected ocean warming on [..] two copepods. Progress in Oceanography. DOI: 10.1016/j.pocean.2010.09.013
This group has prepared many interesting studies on the impact of climate change for different plant species and regions. You may also have a look into journals like Global Change Biology or Global Ecology and Biogeography. They frequently publish studies on this matter.
Best Bioindicator for investigation the effect of climate change on aquatic ecosystems are respectively: Algae, Zooplankton and fishes. In my opinion, in these systems Algae and Zooplankton especially Copepoda ( To assessing Long-term changes); and fishes (Long-term changes) are very useful.
We need to know and justify why we choose a specific species as a bio-indicator. As you know, different species could react differently to single environmental change. No single species can be said to best to describe the whole events caused by climate change. Look at the criteria for selecting suitable bio-indicator.
In addition to phenological change, distributive change (at a species level) is useful, especially in temporate zones. In the UK, a lot of the focus has been on Odonata and aquatic heteroptera. I have no specific references for you, but the Wilby et al paper, attached to my profile page, will give you a broad overview for the UK.
Any correctly interpreted piece of knowledge has a good bioindicative value. For climatic changes the ecologicaly well known and richly differentiated groups are to be selected. In addition the effective methods of their collecting is to be considered. Excelent are Mollusc, among the beetles Carabids, among Diptera the male preconnubial aggregations of Sarcophagids, as paritoids of Mollusc or Lumbricid, give excelent responses on enviromental changes
From a California perspective where permanent drought seems to be the new normal climate, if you look carefully at the ecosystems that have existed for thousands of years and see major changes. For example in forests and grasslands, do you have just old plants and have those ecosystems stopped reproducing? Most of our oak species and what remains of our native perennial grasses are all old plants, and you do not see young seedlings. Also are the ranges shifting? Doing an "age-pyramid" study on your trees and perennial grasses can be a good indicator.
And what is happening to the annual and herbaceous perennials (i.e. wildflowers) and grassland understory in general--is it losing ground or absent? World-wide we are losing the wildflowers, native annuals and herbaceous perennials which used to comprise around 100 species in any part of the planet, and our domesticated animal grazing is truncating the number of species worldwide. Doing vegetation cover and species diversity surveys of the native understory can also be a good indicator of changes.
Climate Forcing. Climate forcing refers to a change in the Earth's energy balance, leading to either a warming or cooling effect. An increase in the atmospheric concentrations of greenhouse gases produces a warming effect over time. How does climate change affect animals and plants?
Plants, Animals, and Ecosystems. Most plants and animals live in areas with very specific climate conditions, such as temperature and rainfall patterns, that enable them to thrive. Any change in the climate of an area can affect the plants and animals living there, as well as the makeup of the entire ecosystem.
As greenhouse gases trap more energy from the sun, the oceans are absorbing more heat, resulting in an increase in sea surface temperatures and rising sea level. Changes in ocean temperatures and currents brought about by climate change will lead to alterations in climate patterns around the world. Some indicators are directly linked to human activities that cause climate change, such as Global Greenhouse Gas Emissions. Changes depicted by other indicators, such as U.S. and Global Temperature, have been confidently linked with the increase in greenhouse gases caused by human activity.
Following are Clear Indicators Our Climate is Changing:;
Air temperatures over land are increasing.
Arctic sea ice is decreasing.
Glaciers are melting.
Sea levels are rising.
Ocean heat content is increasing.
Sea surface temperature is increasing.
Snow is decreasing.
Earth's lower atmosphere temperature is increasing.