A subspecies, Calumma parsonii cristifer is recognized from around Analamazaotra and Mantadia. At least three distinct colour morphs from different localities are also known (Brady and Griffiths 1999).

Listed as Near Threatened based on a past population decline greater than 15-20%, and potentially close to 30%, over the past 15-18 years (assuming a generation length of 5-6 years), thus making the species close to qualifying for Vulnerable under Criterion A2bd. This decline is due mainly to habitat loss driven by slash-and-burn agriculture and other threats operating across its large range, however large-scale off-take of wild individuals in the final years of legal trade is likely to have been a localized contributor to declines. Recent population trends in this apparently rare chameleon should be quantified where possible, as the loss of adult individuals through historical over-collection may have impaired the chameleon's ability to withstand the effects of habitat loss, and more detailed population data may reveal that the species should be listed in a more threatened category.

This large chameleon species is found in the humid eastern part of Madagascar, from Ranomafana in the south to Anjanaharibe Sud in the north (Rakotomalala and Raselimanana 2003) and the Masoala Peninsula (F. Andreone pers. comm. January 2011). It has also been recorded from Manongarivo in the northwest (Raxworthy 2003). There is also a population on Nosy Boraha (Glaw and Vences 2007). It has been reported from elevations between 45-230 m (Rabearivony et al. 2008), from 1,100 m (Rakotomalala and Raselimanana 2003, D. Rakotomalala pers. comm. January 2011) and from 1,195 m in Masoala (F. Andreone pers. comm. January 2011). This widespread lizard has an estimated extent of occurrence of 39,800 km².

This large chameleon consistently occurs in lower population densities than other Calumma species (Brady and Griffiths (1999) although this might be because Parson's chameleon roosts in elevated locations in the canopy out of reach of nocturnal surveys by torch light. The species was notably scarce in low elevation forest at Ambodiriana (Rabearivony et al. 2008). Brady and Griffiths (1999) reported densities of between 1.3 ha^-1 and 3.9  ha^-1 in relatively intact forest at Parc National de Mantadia, with lower densities (0.1-0.4 ha^-1) in more disturbed forest in the same area. It is rarely encountered even by workers spending weeks in suitable habitats, and adults appear to be especially scarce (R. Jenkins pers. comm. June 2011).

Although no more recent figures are available, between 1990 and 2000 humid forest cover in Madagascar declined by 0.8% a year (Harper et al. 2007); however this figure may underestimate forest loss within the range of Parson's chameleon, as it does not distinguish the lowland forest preferred by this lizard, and which is under greatest pressure, from humid forest at higher elevations. As rates of forest loss in Madagascar are increasing (Harper et al. 2007), and remaining forest increasingly occurs as fragments which may be too small to sustain viable populations of this large lizard, this species may have experienced a population decline somewhat greater than implied by this figure over the previous three generations (15-18 years), especially when also accounting for the effects of over-collection. The population is presumably still declining due to its observed scarcity in disturbed habitats and the ongoing loss and degradation of forest throughout its range, although the ban on trade in this species might have resulted in local increases in abundance at former collecting localities (F. Rabemananjara pers. comm. June 2011).

Rabearivony et al. (2008) found Parson's chameleon in low abundance in a lowland forest in the northeast. Glaw and Vences (2007) report that Calumma p. cristifer is regularly found on high branches.  Glaw and Vences (2007) report that this species is frequently seen along forest streams, although Brady and Griffiths (1999) suggest that only hatchlings are associated with water. It is reportedly difficult to find during the austral winter in northern Madagascar (Andreone et al. 2000). In captivity, 20-30 eggs are buried and hatch after 400-520 days. This species, the world's largest chameleon by weight, might be very long lived for a chameleon, with ages of six years recorded and 10-12 expected. Captive specimens may live somewhat longer, with ages of at least 14 recorded (in one case, an animal of this age died prematurely due to an equipment failure), and a maximum longevity of 20 years has been suggested (R. Jenkins and C.V. Anderson, pers. comms. June 2011). Sexual maturity may be reached as early as 1.5 years (LeBerre 1995), but Brady and Griffiths (1999) noted reports from captive chameleons that three to five is more likely.

The extent to which this species requires intact humid forest remains unresolved; while evidence suggests that it is more abundant in less disturbed forest (Brady and Griffiths 1999, Raxworthy 1988) it is also found in disturbed sites (Brady and Griffiths 1999, Glaw and Vences 2007), including high trees in villages (F. Rabemananjara pers. comm. June 2011).

The loss of humid forest, mainly through conversion from slash-and-burn agriculture but also due to logging, is a threat to this species. Much of the habitat of this species is extremely fragmented, and small forest fragments are unlikely to be viable to ensure persistence of this large chameleon that occurs at low densities. A resumption of trade could pose a threat to local populations if collection was not properly managed.

This was was the most frequently traded chameleon species from Madagascar before the CITES trade suspension in 1995, with exports peaking in the early 1990s shortly before the ban (Carpenter et al. 2004). Carpenter et al. 2004 report that, at the time of their study, the chameleon had only been traded in very low numbers since 1995. However, a TRAFFIC investigation in Thailand, which focused on the trade in Malagasy chameleons since 2004, found Parson's chameleon to be "widely traded", with 28 specimens (of a total of 115 Calumma individuals) recorded in illegal trade in January 2010 (Todd, 2011)

Parson's Chameleon is found in a number of strict protected areas, from where all wild animal collection in Malagasy national parks is illegal. This species is listed as Category I, Class II protected species in Malagasy law, which prohibits unauthorized collection. This species is listed on Appendix II of CITES but imports from Madagascar were suspended in 1995. There are no formally established captive-breeding programmes for this species. It needs to be established whether illegal collection represents a threat to this species, and any harvest should be monitored. As this species is unlikely to persist in small forest fragments, efforts should be made to manage areas where it occurs to maximize connectivity between forest patches. Research is needed to clarify this species' life history in the wild, and to improve estimates of generation length.