Table 1.

Case studies illustrating mechanistic links connecting climate, biodiversity, and infectious disease. A) Climate → Biodiversity → Infectious disease B) Climate → Infectious disease → Biodiversity C) Infectious disease → Biodiversity → Climate D) Biodiversity → Climate → Infectious disease E) Biodiversity → Infectious disease → Climate F) Infectious disease → Climate → Biodiversity. Each pathway is discussed in further details in section Mechanistic Links.

A) Climate → Biodiversity	Biodiversity → Disease	Case Study	Pathway
Precipitation & Food web dynamics	Dilution / Amplification	Elevated precipitation increases resource production, which in turn increases reservoir species richness and abundance, amplifying Lyme disease.201–206
		Addition of host species with low reservoir competence to a community with low species richness reduces Borrelia burgdorferi infection in nymphal ticks, and thus Lyme disease prevalence.207,208
	Vector population	Drought induced changes in water depth and patchiness, disrupting aquatic food webs, and control of larval mosquitoes by fish.209 The increase in mosquito populations210 and the concentration of avian hosts around remaining watering holes211 increases West Nile virus transmission.
Temporal mismatch	Migration	Climate induced shifts in the phenology of milkweed, leading to changes in Monarch butterfly migration, which acts as a filter for diseased individuals—disease prevalence is higher at the end of breeding season than at overwintering sites.212
Gradual climate change & Species introductions	Novel disease spread	Permafrost melt releases active bacteria and viruses from thawing carcasses, leading to anthrax outbreaks.95,213
Migration / Range shifts	Spillover	Change in migratory behavior of harp seals following increased sea ice melt, increased opportunities for disease spillover and outbreaks of phocine distemper.96,214–215
	Dilution / Amplification	Sea ice melt alters the migration of caribou, a seasonal disease escape strategy. Increased contact between geographically separated ungulate species, facilitating spillover of diseases into communities that were previously isolated.96
		Extreme wetness and dryness decrease richness of insect-pollinated plants, reshaping the distribution of their pollinators.216 Increased length of pollinator foraging distances, and floral trait variation drive increases in pathogen transmission and disease intensity.217
B) Climate → Disease	Disease → Biodiversity	Case Study	Pathway
Novel disease spread & Spillover	Trophic cascade	Severe storms and warmer water are associated with amoebiasis outbreaks in sea urchins.218 Mass mortality of sea urchins releases kelp forests from predation,219,220 increasing local species richness.221
Thermal mismatch	Parasite mediated competition	Shorter winters favor temperature dependent growth of Geomyces destructans,222 which is linked to White Nose Syndrome (WNS) in bats.223 WNS reduces the abundance of dominant bat species in the community,224 favoring less dominant bat species.
	Extirpation	Cold-adapted and warm-adapted amphibian hosts are more susceptible to Batrachochytrium dendrobatidis (Bd) fungus at relatively warm and cool temperatures, respectively.86 Bd infection has caused amphibian population declines and extirpation.135,136
		Climate related shifts in habitat suitability for white pine blister rust resulted in a decline in prevalence in arid regions and an increase in colder regions—causing extirpation.178
Temperature & Physiology	Species decline	Temperature dependent virulence of Vibrio spp.,105 which are associated with coral bleaching and disease.225 Coral declines are associated with fish biodiversity loss.226
		Warming temperatures increase the occurrence and severity of Ranavirus,227 a disease linked to mass mortality events and population declines in the common frog.228
Behavior		Drought increased foraging distances in the blue orchard bee, resulting in the increase of parasitism rates by the blister beetle and subsequent species decline.229,230
Development time of pathogens	Extirpation	Decreased larval development times of the lung-dwelling nematode, Umingmakstrongylus pallikuukensis, of muskoxen (Ovibos moschatus) increases infection pressure,231 which cascades to elevated predation risk from polar bears.232
Novel disease spread & Spillover		Shifts in timing of end of the dry season when Ebola outbreak risk is highest.233–235 Mortality induced changes in local primate community assemblages.236,237
C) Disease → Biodiversity	Biodiversity → Climate	Case Study	Pathway
Species decline / Extirpation	Ecosystem services	The loss of keystone and mesopredators due to Sea star wasting disease (SSWD) reduces kelp forest resilience.238,239 Loss of kelp forest could reduce potential to capture and store (blue) carbon.240,241
		Eelgrass wasting disease and loss of eelgrass beds159,242 may reduce potential carbon sequestration.243
		The chestnut blight fungus, native to East Asia, effectively removed a dominant forest tree in the Eastern US.177,244 The death and decay of mature American chestnuts resulted in a pulse of released carbon and removed an important carbon sink.245
		Haplosporidium nelsoni (MSX) influences shellfish populations, and epizootic outbreaks have led to large population declines.246 Oyster beds provide a range of ecosystem services, including habitat for fish, water filtration, and shoreline protection.247,248
	Trophic cascade	Rinderpest reduced herbivore density in the Serengeti. Decreased grazing released vegetation from top-down control and increased fires, shifting the habitat to a net carbon source.249,250
Parasite mediated competition	Ecosystem services	Foliar fungal pathogens increase plant biodiversity by reducing above ground plant biomass.251 Reduced biomass may decrease ecosystem services, including carbon sequestration; however, more diverse grasslands are suggested to sequester more carbon.252
D) Biodiversity → Climate	Climate → Disease	Case Study	Pathway
Deforestation	Development time of pathogens	Deforestation effects on microclimate may increase local warming, shortening the development time of Plasmodium falciparum within their mosquito vector, increasing malaria risk.253
Urbanization	Development time of vectors	Land use change, industrialization, and replacement of vegetation with heat absorbing surfaces, such as roads and buildings, can lead to urban heat islands. 46,254–260 Warmer local temperatures can shorten the development time of disease vectors,261 increasing disease transmission.84
E) Biodiversity → Disease	Disease → Climate	Case Study	Pathway
Species introductions & Novel disease spread	Ecosystem services	Introduced non-native species and their pathogens, i.e., Cryptococcus fagisuga causing beech bark disease,261,262 can result in tree damage and death, reducing forest biomass and potential carbon sequestration capabilities.263
Dilution / Amplification		Tree diversity has a hump-shaped relationship with pest diversity (at low tree diversity pests are amplified and at high tree diversity pests are diluted).264 Mountain pine beetle infestation reduces forest biomass and carbon sequestration capabilities. 265
F) Disease → Climate	Climate → Biodiversity	Case Study	Pathway
Behavior	Ecosystem services	Parasitic plants, such as Striga hermonthica—a parasite of sorghum-–may modify their microclimate via high transpiration rates. 266 Forest microclimate influences soil microbial composition, impacting primary productivity, and plant communities. 267
	Climate-induced biodiversity decline (various mechanisms)	The mitigation strategies used at the emergence of COVID-19 (travel bans, social distancing, suspended industrial production) also mitigated climate change by decreasing daily CO2 emissions.110,111,268