SAJC Cluster 3.2 Lecture 11 notes (Possible Effects of Contemporary Climate Change (I):)

St Andrew’s Junior College H2 Cluster 3: Sustainable Future and Climate Change H2_Cluster 3 Lecture 11_2025/pg1 Lecture 11 Possible Effects of Contemporary Climate Change (I): Impacts on Ecosystems and Humans KEY QUESTION: How will contemporary climate change impact humans? Will contemporary climate change impact everyone in the same way? With the completion of this lecture, attached readings and tutorial, you should be able to understand the: • Changes in temperature and precipitation associated with contemporary climate change • Impacts of contemporary climate change on aquatic and terrestrial ecosystems • Impacts of these changes in aquatic and terrestrial ecosystems on humans • Impacts of contemporary climate change on places • Variation in negative impacts of contemporary climate change Lecture Overview 11.1 Changes in Temperature and Precipitation associated with Contemporary Climate Change (a) Temperature (b) Precipitation 11.2 Impacts of Contemporary Climate Change on Ecosystems (a) Terrestrial ecosystem (b) Aquatic ecosystem Box 1: Contemporary climate change and its impacts on walruses 11.3 Impacts of Changes to Ecosystems on Humans 11.4 Positive and Negative Impacts of Contemporary Climate Change on Places 11.4.1 Melting Ice Sheets and Sea Level Rise (SLR) 11.4.2 Extreme Weather – (a) Desertification and Drought (b) Storms and Cyclones 11.4.3 Human Health 11.4.4 Migration of Populations 11.4.5 Crop Yields 11.4.6 Trade Routes 11.4.7 Tourism 11.5 Variations in Negative Impact of Contemporary Climate Change 11.5.1 Variations in Negative Impacts of Contemporary Climate Change due to Places 11.5.2 Variations in Negative Impact of Contemporary Climate Change due to Differences in Vulnerability of Different Groups of People 11.6 Conclusion Readings – The following are recently published summaries of the impacts observed in world regions most relevant in our syllabus: 1) Geofile 770, January 2018: See the Great Barrier Reef before you die … or before it dies? 2) IPCC AR6 (2022) Factsheet – Asia 3) IPCC AR6 (2022) Factsheet – Africa 4) IPCC AR6 (2022) Factsheet – Small Islands

St Andrew’s Junior College H2 Cluster 3: Sustainable Future and Climate Change H2_Cluster 3 Lecture 11_2025/pg2 11.1 Changes in Temperature and Precipitation associated with Contemporary Climate Change • In Lecture 10, we learnt that the enhanced greenhouse effect has led to an increase in heat that is retained on Earth, bringing about an increase in global average temperatures. The rise in temperature influences precipitation. Together, the increase in temperature and precipitation changes are expected to generate potentially devastating impacts on natural systems and humans as a result. (a) Temperature • As we have learnt in earlier lectures, the increased amounts of greenhouse gases released by human activities have enhanced the natural greenhouse effect, causing global temperatures to rise. • To date, human-generated emissions since the start of the Industrial Revolution have led to global warming of 1.0°C. • If these emissions continue at current rates, we are likely to reach 1.5°C of warming between 2030 and 2052 – an additional warming of 0.5°C from today’s level (see Fig. 1). Fig. 1

St Andrew’s Junior College H2 Cluster 3: Sustainable Future and Climate Change H2_Cluster 3 Lecture 11_2025/pg3 (b) Precipitation • A warmer atmosphere can hold more moisture, and globally water vapour increases by 7% for every degree centigrade of warming. How this will translate into changes in global precipitation is less clear cut, but the total volume of precipitation is likely to increase by 1- 2% per degree of warming. o But this increased moisture will not fall evenly across the planet. Some areas will see increased precipitation, while other areas are expected to see less due to shifting weather patterns and other factors. o It is also likely that in a warmer climate, heavy rainfall will increase and be produced by fewer more intense events. This could lead to longer dry spells (in between these rainfall events). • Fig. 2 below shows projected percentage change in precipitation between the current climate (represented by the 1981-2000 average) and the end of the century (2081-2100) in the average of all of the climate models featured in a recent IPCC report, using the business-as- usual scenario. • Purple colours show areas where precipitation will increase, while orange areas indicate less future rain and snow. On average, warming is expected to result in dry areas becoming drier and wet areas becoming wetter, especially in mid- and high-latitude areas. Fig. 2 11.2 Impacts of Contemporary Climate Change on Ecosystems • Impacts of contemporary climate change can be seen on natural and human systems (see Fig. 3). For the purpose of this lecture, we focus on the natural systems, specifically terrestrial and aquatic ecosystems respectively (see Section 11.2) and also impact of changes to ecosystems on humans (see Section 11.3). • An ecosystem can be defined as a dynamic complex of plant, animal and microorganism communities and the non-living environment interacting as a functional unit. Humans are an integral part of ecosystems.

St Andrew’s Junior College H2 Cluster 3: Sustainable Future and Climate Change H2_Cluster 3 Lecture 11_2025/pg4 • Climate is a key element of ecosystems, shaping habitats that support plants and animals. Some plant and animal species will adapt to change, others, more highly specialised or geographically isolated, face decline and ultimately extinction. • Many terrestrial, freshwater, and marine species have also shifted their geographic ranges, seasonal activities, migration patterns, and species interactions in response to ongoing climate change. (a) Terrestrial ecosystem • A terrestrial ecosystem is a land-based community of organisms and the interactions of biotic and abiotic components in a given area. • Climate, primarily temperature and precipitation, determine the geographic distribution of major terrestrial ecosystems from deserts to rain forests. Forests and other terrestrial biomes provide habitats for a diversity of plants and animals. If the forest is damaged or removed, habitat loss can endanger the survival of the associated living organisms. Climate change can directly affect many plants and animals by altering the growing season or temperature patterns that trigger life cycle changes. • The impacts on ecosystems are possibly more apparent in the tundra (i.e. the Arctic region where the subsoil is permafrost, or permanently frozen) than in any other ecosystems, as temperatures are rising fastest there. Examples of habitat change include: Fig. 3

St Andrew’s Junior College H2 Cluster 3: Sustainable Future and Climate Change H2_Cluster 3 Lecture 11_2025/pg5 o As the permafrost thaws, wetland areas expand, attracting more migratory birds. Influxes of spring migrants from the south will occur earlier, the breeding season will last longer and higher temperatures will ensure an abundance of insects. o Meanwhile, the southern fringes of the tundra will lose their open aspect as the tree line advances north. As forests replace tundra, changes in habitat will affect indigenous plant and animal species. Migration patterns among animals such as the caribou (a type of reindeer), which spend the summer on the tundra, will be disrupted. As open tundra habitats shrink, predators such as snowy owls and arctic foxes, which r