Climate Science, Ecology & Conservation

Environmental science integrates atmospheric physics, ecology, chemistry, and policy to understand Earth's interconnected systems. This pack covers the core mechanisms of climate change, ecosystem dynamics, biodiversity loss, and evidence-based conservation strategies.

## Climate System Fundamentals

Earth's energy budget drives everything. Incoming SWR (shortwave radiation) from the sun (~340 W/m²) is partially reflected by ALB (albedo — clouds, ice, surfaces reflecting ~30%) and partially absorbed. The surface re-emits LWR (longwave radiation/infrared). GHGs (greenhouse gases) absorb and re-emit LWR in all directions, warming the lower atmosphere. Without the natural GHE (greenhouse effect), Earth's average temperature would be -18°C instead of +15°C.

The enhanced GHE from anthropogenic GHG emissions is the driver of modern CC (climate change). CO2 concentrations have risen from 280 ppm (pre-industrial) to over 420 ppm. CH4 (methane) is 80x more potent than CO2 over 20 years but has a shorter ATL (atmospheric lifetime) of ~12 years versus CO2's centuries-to-millennia persistence. N2O (nitrous oxide) from agriculture has 273x the GWP (global warming potential) of CO2 over 100 years.

CF (climate forcing) measures the energy imbalance caused by a factor. Positive CF warms (GHGs, black carbon), negative CF cools (aerosols, increased ALB). Current net anthropogenic CF is approximately +2.7 W/m², with CO2 contributing +2.2 W/m². The planet has warmed ~1.2°C above pre-industrial baseline.

## Feedback Mechanisms

FBL (feedback loops) amplify or dampen initial warming. Positive FBLs accelerate change:

ICE-ALB FBL: warming melts ice → darker ocean/land exposed → lower ALB → more SWR absorbed → more warming. The Arctic has warmed 3-4x faster than the global average (Arctic amplification), losing ~13% of summer sea ice per decade.

WVF (water vapor feedback): warmer air holds more H2O (7% per °C, Clausius-Clapeyron). Water vapor is itself a potent GHG, roughly doubling the warming from CO2 alone. This is the single largest positive FBL.

PRM (permafrost) thaw: Arctic PRM contains ~1,500 GT of organic carbon — twice the atmospheric total. As PRM thaws, microbial decomposition releases CO2 and CH4. Some estimates suggest 5-15% of PRM carbon could be released by 2100 under high-emission scenarios, creating a self-reinforcing warming cycle.

Negative FBLs provide some stabilization: PLK (Planck response — warmer surfaces emit more LWR), LPS (lapse rate feedback in tropics), and increased cloud ALB in some regions. But positive FBLs currently dominate.

## Ocean Systems

Oceans have absorbed ~90% of excess heat and ~30% of anthropogenic CO2. This buffering has slowed atmospheric warming but at enormous cost.

OCA (ocean acidification): dissolved CO2 forms carbonic acid, lowering pH. Surface ocean pH has dropped from 8.2 to 8.1 (a 30% increase in hydrogen ion concentration). Below pH ~7.8, aragonite (the calcium carbonate form used by corals, pteropods, and shellfish) becomes undersaturated — organisms cannot build shells. Coral reef systems face combined stress from BLC (bleaching — thermal expulsion of symbiotic zooxanthellae) and OCA.

THC (thermohaline circulation) — the global ocean conveyor belt driven by temperature and salinity gradients. Cold, salty water sinks in the North Atlantic (NADW — North Atlantic Deep Water formation), driving global heat distribution. Greenland ice melt adds freshwater, reducing salinity and potentially weakening AMOC (Atlantic Meridional Overturning Circulation). AMOC weakening would paradoxically cool Western Europe while warming continues globally, and shift tropical rainfall patterns.

SLR (sea level rise) has two components: thermal EXP (expansion — warmer water occupies more volume, ~50% of current SLR) and ice mass loss (Greenland + Antarctic ice sheets + glaciers, ~50%). Current rate: ~3.7 mm/year, accelerating. Projections: 0.3-1.0m by 2100 under moderate scenarios; >1m under high-emission. Tipping points in West Antarctic Ice Sheet could add 3-5m over centuries.

## Ecosystem Ecology

Ecosystems function through energy flow and nutrient cycling. NPP (net primary productivity) — the rate at which plants convert solar energy to biomass minus their own respiration — drives all food webs. Global terrestrial NPP is ~120 GT carbon/year; oceanic NPP ~50 GT carbon/year.

BGC (biogeochemical) cycles connect living and non-living systems. The carbon cycle: atmospheric CO2 → photosynthesis → biomass → decomposition/respiration → atmosphere. Human disruption: fossil fuel combustion and LULC (land use/land cover change — mainly deforestation) release ~11 GT carbon/year; natural sinks absorb ~5.5 GT; remainder accumulates in atmosphere.

The nitrogen cycle: atmospheric N2 → BNF (biological nitrogen fixation) by bacteria → ammonium → nitrification → nitrate → plant uptake → decomposition → denitrification back to N2. The Haber-Bosch process has doubled global reactive nitrogen, causing EUT (eutrophication — nutrient overload in water bodies → algal blooms → oxygen depletion → dead zones). The Gulf of Mexico hypoxic zone covers ~15,000 km² annually.

## Biodiversity & Conservation Biology

BDV (biodiversity) operates at three levels: genetic, species, and ecosystem. Current extinction rates are 100-1000x the background rate — we are in Earth's sixth mass extinction event.

The five drivers of BDV loss (HIPPO framework): HAB (habitat) loss and fragmentation (#1 driver — ~75% of terrestrial surface significantly altered), INV (invasive species), POL (pollution), POP (human population/overconsumption), and OVX (overexploitation — overfishing, poaching, wildlife trade).

ISB (island biogeography theory, MacArthur & Wilson): species richness on islands is determined by immigration rate (decreases with distance from mainland) and extinction rate (increases with smaller area). This theory underpins modern conservation: habitat fragments function as islands. The SAR (species-area relationship: S = cA^z) predicts that a 90% HAB reduction eliminates ~50% of species.

MVP (minimum viable population): the smallest population size that can survive long-term stochastic events. Below MVP, populations face extinction vortex — small population → inbreeding → reduced fitness → smaller population. For most vertebrates, MVP is 500-5000 individuals. EFP (effective population size) — the breeding subset — is typically 10-30% of census population.

Conservation strategies must operate at landscape scale. COR (corridors) connecting protected areas allow gene flow and migration. Buffer zones reduce edge effects. PA (protected areas) currently cover ~17% of terrestrial and ~8% of marine area; the 30x30 target (30% by 2030) requires massive expansion, especially in underrepresented biomes (grasslands, deep sea, freshwater).

## Mitigation & Adaptation

MTG (mitigation) reduces GHG emissions or enhances sinks. The carbon budget for 1.5°C warming: ~400 GT CO2 remaining (at current rates, exhausted by ~2030). For 2°C: ~1,150 GT.

Sector solutions: energy (80% of emissions) — transition from FF (fossil fuels) to RNW (renewables: solar, wind, hydro, geothermal) + nuclear + storage. Transport — electrification + mass transit. Industry — process efficiency + CCS (carbon capture and storage) + hydrogen. Agriculture — reduced CH4 from livestock, improved NM (nitrogen management), agroforestry. LULC — halt deforestation + reforestation/afforestation.

NBS (nature-based solutions): protecting and restoring ecosystems that sequester carbon. Tropical forests, mangroves, peatlands, seagrass meadows. Mangroves sequester 3-5x more carbon per hectare than terrestrial forests. Peatlands hold 30% of soil carbon on 3% of land area.

ADP (adaptation) prepares for unavoidable impacts: flood infrastructure, drought-resistant crops, heat-resilient urban design, managed retreat from coastlines, early warning systems. Effective ADP is equitable — vulnerable populations (low-income, Indigenous, island nations) contribute least to CC but bear greatest impact.