IELTS General Reading Practice Test 2 Online – Free General Training Test

Paragraph A: Coral reefs, often termed the “rainforests of the sea,” represent some of the planet’s most biologically diverse and productive ecosystems. Despite covering less than 0.1% of the ocean floor, they support roughly **25%** of all marine life. However, these intricate, calcified structures are facing an unprecedented global collapse, driven primarily by **anthropogenic climate change**. The mechanisms of decline are complex and mutually reinforcing, centred around **rising sea temperatures** and **ocean acidification**. The rapid acceleration of this decline should be viewed not just as an ecological catastrophe, but as a dire warning regarding the fundamental stability of the marine biome.

Paragraph B: Rising sea temperatures, even slight increases beyond the established seasonal maximum, are the direct cause of **coral bleaching**. This process occurs when stressed coral polyps expel the **symbiotic algae, zooxanthellae**, living within their tissues. The zooxanthellae provide the coral with its vibrant colour and, crucially, up to **90%** of its energy through photosynthesis. While bleached coral is not immediately dead, prolonged bleaching leaves it starving and highly susceptible to disease. Mass bleaching events, once rare, have become routine, affecting nearly all major reef systems, including the Great Barrier Reef, since the late 20th century. I contend that the persistent focus on **local pollution controls**, while **necessary**, distracts from the overarching and decisive influence of global thermal stress.

Paragraph C: A simultaneous, equally severe threat is **ocean acidification**. The ocean absorbs approximately one-third of the **carbon dioxide ($\text{CO}_2$)** emitted by human activities. This absorption lowers the water’s $\text{pH}$—a change which, though small in absolute terms, has profound implications for calcifying organisms. Corals, as well as mollusks and plankton, require **calcium carbonate** to build and maintain their skeletons and shells. Acidification makes the required form of carbonate ions less available, making it energetically expensive for corals to calcify and leading to reduced growth rates and increased skeletal fragility. Some scientists argue that natural **ocean buffering mechanisms** will eventually compensate for the $\text{pH}$ drop. However, I believe that the **current speed of $\text{CO}_2$ addition** far outpaces the ocean’s natural capacity for remediation, rendering this counterargument dangerously complacent.

Paragraph D: The implications of reef loss extend far beyond biodiversity. Reefs provide vital coastal protection, dissipating wave energy and reducing the impact of **storm surges** on vulnerable coastlines. Economically, they underpin lucrative fishing industries and the global **ecotourism** sector, which generates billions of dollars annually. The disappearance of reefs would therefore initiate a complex ripple effect: increased coastal erosion, **food insecurity** for dependent **coastal communities**, and significant economic destabilisation. The challenge for conservation science has thus shifted from preservation to active restoration and adaptation. Techniques such as **coral gardening** and **assisted evolution** are being explored. It is my opinion that these restoration efforts, while laudable, represent a form of **palliative care** unless they are coupled with **radical, global $\text{CO}_2$ emission reduction**. The idea that we can engineer our way out of the crisis—for example, through geoengineering techniques like solar radiation management—is a scientifically questionable proposition that avoids confronting the root cause. Ultimately, the rapid decline of reefs serves as a critical indicator of our planet’s ecological tolerance limits. Their fate is inextricably linked to our energy choices, making reef conservation a proxy for the success of global climate policy.