Are Human Land Uses Becoming Too Hot to Handle?

March 10, 2020

Almost 3 years ago I started my PhD with the aim to explore the impacts of habitat change on wildlife, specifically focusing on how animals are affected by the changes in temperature and rainfall following land changes. At the end of last year, I published a paper (yay!) aimed at answering this question. Here, I am going to give you a breakdown of why this topic is important, what I found out and the implications this has for wildlife (basically, the interesting and important parts)! So, let’s begin…

 

The background

The number of humans on Earth is rapidly increasing – by 2050 there will be an estimated 9.7 billion of us (1)! Consequently, the demand for food, water, building materials and other resources is also growing. These demands lead to greater areas of land being transformed (as seen below) away from their natural state (e.g. forests and grasslands) into human-altered land uses, such as croplands, pastures, plantations or urban areas.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Habitat change and loss currently pose the greatest threat to wildlife (2). The transformation from natural to human land uses not only destroys animal’s homes, it can also remove food sources, cut off migration paths and force animals to live closer together (increasing levels of conflict between individuals – imagine you and your neighbours suddenly having to share one house; I can definitely see this leading to arguments!).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

There has been a lot of research looking at these impacts of habitat transformation. However, more recently, another impact of land conversion has come into scientists’ focus (3). When natural habitats are transformed by humans, to agriculture or urban areas for example, it also changes the local climate (4,5).

Let’s go on a quick little adventure: imagine yourself walking through a woodland on a hot, sunny day. If you’re underneath the shade of the canopy layer, it’s cool, and you can walk comfortably without overheating. Now imagine you come to the edge of the forest and step out into an open cornfield where the hot sun is glaring down on you. Here, you’ll likely feel hotter and the ground may feel harder and drier. When deciding where to have your picnic, if I were you, I’d go back into the shade of the woodland canopy.

Coming back to reality, human land uses are hotter and drier than natural habitats on average (5). The lack of a canopy layer (the trees keeping you cool in the woodland) means that human land uses often have hotter maximum temperatures and colder minimum (night-time or winter) temperatures (6). In addition, land conversion to human land uses also changes the vegetation present, which impacts processes such as evapotranspiration (water transfer from the land and plants into the atmosphere) and thus the amount of rainfall in the local area (7). I wanted to find out what impacts these changes in local climate have on the wildlife in these human land uses. Personally, I would like it if my local area had less rain and was generally hotter – but is it the same for wildlife?! What if some animals are not able to tolerate these changes in temperature and rainfall? I know if I had to sleep outside overnight, I would not want it to get even colder!

 

 

 

 

 

 

 

 

 

 

 

 

The impacts of these local climatic changes…    

In the analysis I carried out (along with Tim Newbold and Amanda Bates), we found that, on average, animals living in human-altered land uses (croplands, pastures and plantations) can tolerate more extreme climates compared to animals in natural habitats (8). So, what does this mean? 

 

Well, it appears that croplands, pastures and plantations are favouring certain species, specifically those that can tolerate hotter maximum temperatures, colder minimum temperatures, wetter and drier extremes of precipitation. Observations in the field have also found this (5,9). For example, a study focusing on tropical amphibians found that frogs from areas transformed by humans (e.g. pastures) were able to tolerate hotter temperatures than species only found in forests (9). Consequently, it appears that species not able to tolerate such extremes of climate are being more negatively impacted by human land uses­ (8).

 

Why is this happening?

It’s likely that local climatic changes following land conversion (increases in hot and cold extremes and changes in rainfall patterns) are impacting wildlife in these areas both directly and indirectly (3).

 

Directly, if animals are not able to cope with the new climate (i.e. they overheat or can’t survive the cold extremes), they will not be able to continue living in that area (they will have to migrate to another habitat or they may die) (10). Thinking back to our woodland walk, if you decided to have your picnic in the cornfield, but then started to get too hot, you would probably move back into the shade of the trees. 

Indirectly, the changes in temperature or rainfall may impact the food sources available in the area, other species in the community (e.g. predators or competitors) or the availability of other resources (such as nest building materials), which may lead to some species no longer being able to live in that habitat (11,12).

 

Is this concerning?

Yes! These changes in temperature and rainfall are adding to the long list of impacts facing wildlife when humans convert natural habitat for their own use. The local climatic changes are leading to changes in the variety and abundance of species present (8). In a nutshell, the changes favour some species while making the area uninhabitable for others. Biodiversity is very important for ecosystem functioning: animals and plants help to maintain critical processes (pollination, fresh water production, disease and pest regulation), which are key to human well-being (13). When the structure of natural systems is impacted and reshaped by human action, it can have knock-on effects for ecosystem functioning and the benefits we get from nature (13).

ConCon Conclusion

The local climatic changes following land conversion from natural to human-altered land uses are impacting the species able to live within these areas. Specifically, human land uses, such as croplands, plantations and pastures, are favouring species able to tolerate more extreme climatic conditions (both temperature and precipitation levels). As the human population grows, and their demands for resources increase, it is critical that scientists and conservationists understand the effects of pressures such as habitat change and loss on animals, in order to design appropriate and effective management schemes and mitigate the shifts in local climatic conditions.

 

 

Dying to know more about this research? We thought so. 

 

Check out the original research paper:https://onlinelibrary.wiley.com/doi/full/10.1111/ecog.04806), read a review on the topic (https://onlinelibrary.wiley.com/doi/full/10.1111/ddi.12999), or check out the references below! 

 

References 

1 United Nations, Department of Economic and Social Affairs, Population Division (2019). World population prospects 2019: Ten key findings. 

 

2 WWF (2014). Living Planet Report 2014: species and spaces, people and places. [McLennan, R., Iyengar, L., Jeffries, B., & Oerlemans, N., (Eds)]. WWF, Gland, Switzerland. 

 

3 Williams, J. J., & Newbold, T. (2019). Local climatic changes affect biodiversity responses to land use: A review. Diversity and Distributions, 26, 76-92. doi: 10.1111/ddi.12999

 

4 Britter, R., & Hanna, S. (2003). Flow and dispersion in urban canopies. Annual Review of Fluid Mechanics, 35, 469-496. doi: 10.1146/annur ev.fluid.35.101101.161147

 

5 Frishkoff, L. O., Karp, D. S., Flanders, J. R., Zook, J., Hadley, E. A., Daily, G. C., & M’Gonigle, L. K. (2016). Climate change and habitat conversion favour the same species. Ecology Letters, 19,  1081-1090. doi: 10.1111/ele.12645

 

6 De Frenne, P., Zellweger, F., Rodríguez‐Sánchez, F., Scheffers, B. R., Hylander, K., Luoto, M., … Lenoir, J. (2019). Global buffering of temperatures under forest canopies. Nature Ecology & Evolution, 3(5), 744-749. doi: 10.1038/s41559-019-0842-1

 

7 Sampaio, G., Nobre, C., Costa, M. H., Satyamurty, P., Soares‐Filho, B. S., & Cardoso, M. (2007). Regional climate change over eastern Amazonia caused by pasture and soybean cropland expansion. Geophysical Research Letters, 34(17), 1-7. doi: 10.1029/2007G L030612

 

8 Williams, J. J., Bates, A. E. & Newbold, T. (2019). Human-dominated land uses favour species affiliated with more extreme climates, especially in the tropics. Ecography doi: 10.1111/ecog.04806

 

9 Nowakowski, A. J., Watling, J. I., Whitfield, S. M., Todd, B. D., Kurz, D.J., & Donnelly, M. A. (2017). Tropical amphibians in shifting thermal landscapes under land‐use and climate change. Conservation Biology, 31(1), 96-105. doi: 10.1111/cobi.12769

 

10 Mitchell, D., Snelling, E. P., Hetem, R. S., Maloney, S. K., Strauss, W. M., & Fuller, A. (2018). Revisiting concepts of thermal physiology: Predicting responses of mammals to climate change. Journal of Animal Ecology, 87(4), 956-973. doi: 10.1111/1365-2656.12818

 

11 Porter, W. P., Budaraju, S., Stewart, W. E., & Ramankutty, N. (2000). Calculating climate effects on birds and mammals: Impacts on biodiversity, conservation, population parameters, and global community structure. Integrative and Comparative Biology, 40(4), 597-630. doi: 10.1093/icb/40.4.597

 

12 Bolger, D. T., Patten, M. A., & Bostock, D. C. (2005). Avian reproductive failure in response to an extreme climatic event. Oecologia, 142, 398-406. doi: 10.1007/s00442-004-1734-9

 

13  Naeem, S., Chapin III, F. S., Costanza, R., Ehrlich, P. R., Golley, F. B., Hooper, D. U., … Tilman, D. (1999). Biodiversity and ecosystem functioning: Maintaining natural life support processes. Issues in Ecology, 4, 2-12. 

 

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