Document ID: ./input/supremecourt_opinions/opinions/18pdf/17-71_omjp.pdf
Page Number: 12.0

Cite as:  586 U. S. ____ (2018) 

9 

Opinion of the Court 

phasis  added).  Only  the  “habitat”  of  the  endangered
species is eligible for designation as critical habitat.  Even 
if  an  area  otherwise  meets  the  statutory  definition  of 
unoccupied critical habitat because the Secretary finds the
area  essential  for  the  conservation  of  the  species,  Section
4(a)(3)(A)(i) does not authorize the Secretary to designate
the area as critical habitat unless it is also habitat for the 
species.

The  Center  for  Biological  Diversity  contends  that  the
statutory definition of critical habitat is complete in itself 
and  does  not  require  any  independent  inquiry  into  the 
meaning  of  the  term  “habitat,”  which  the  statute  leaves
undefined.  Brief  for  Intervenor-Respondents  43–49.  But 
the  statutory  definition  of  “critical  habitat”  tells  us  what 
makes  habitat  “critical,”  not  what  makes  it  “habitat.” 
Under  the  statutory  definition,  critical  habitat  comprises
areas  occupied  by  the  species  “on  which  are  found  those 
physical or biological features (I) essential to the conserva-
tion  of  the  species  and  (II)  which  may  require  special 
management  considerations  or  protection,”  as  well  as 
unoccupied  areas  that  the  Secretary  determines  to  be
“essential for the conservation of the species.”  16 U. S. C. 
§1532(5)(A).  That  is  no  baseline  definition  of  habitat—it 
identifies only certain areas that are indispensable to the
conservation  of  the  endangered  species.    The  definition 
allows the Secretary to identify the subset of habitat that
is  critical,  but  leaves  the  larger  category  of  habitat
undefined. 

The  Service  does  not  now  dispute  that  critical  habitat 
must  be  habitat,  see  Brief  for  Federal  Respondents  23, 
although  it  made  no  such  concession  below.    Instead,  the  
Service argues that habitat includes areas that, like Unit 
1, would require some degree of modification to support a 
sustainable  population  of  a  given  species.    Id.,  at  27. 
Weyerhaeuser,  for  its  part,  urges  that  habitat  cannot 
include  areas  where  the  species  could  not  currently  sur-