Opinion
WERDEGAR, J.
We must decide whether two county zoning ordinances relating to the permissible locations for timber operations are preempted by state forestry statutes. Concluding they are not, we reverse the judgment of the Court of Appeal.
Background
In 1999, the Board of Supervisors of the County of Santa Cruz (County) adopted several ordinances that would have affected timber harvesting operations in the County. As pertinent here, County’s ordinances restricted timber harvesting to specified zone districts within the County (Santa Cruz County Res. No. 493-99 & Santa Cruz County Ord. No. 4577 (1999); hereafter the zone district ordinance), barred timber harvesting operations in certain areas adjacent to streams and residences (Santa Cruz County Ord. No. 4571 (1999); hereafter the stream ordinance), and limited the parcels on which helicopter operations associated with such harvesting could occur (Santa Cruz County Ord. No. 4572 (1999); hereafter the helicopter ordinance). County also requested and obtained from the California Coastal Commission a ruling certifying the zone district ordinance as an amendment to County’s local coastal program.
Plaintiffs Big Creek Lumber Co. and Homer T. McCrary (jointly Big Creek) and the Central Coast Forest Association, a nonprofit association of landowners and forestry professionals in the County, filed a petition for writ [1146]*1146of mandate against County and the California Coastal Commission, challenging County’s timber-related ordinances and the Commission’s certification of the zone district ordinance as a local coastal program amendment. Plaintiffs’ petition alleged that County’s and the California Coastal Commission’s actions violated the California Environmental Quality Act (Pub. Resources Code, § 21000 et seq.) and County’s ordinances violated the doctrine of preemption.
The preemption claim was bifurcated and heard separately. The trial court found in favor of plaintiffs except as to the zone district ordinance. On appeal, the Court of Appeal invalidated County’s ordinances in their entirety. We granted County’s petition for review of the Court of Appeal’s invalidation of the helicopter and zone district ordinances.1
Discussion
The zone district ordinance amends County’s zoning laws to restrict timber harvesting operations to areas zoned for timber production, mineral extraction industrial, or parks, recreation and open space. The helicopter ordinance requires that helicopter staging, loading, and servicing facilities associated with timber operations be located either on a parcel of land zoned for timber harvesting or on a parcel adjacent to such, and within the boundaries of a timber harvesting plan that has been approved by the California Department of Forestry and Fire Protection.
Plaintiffs argue that the ordinances are preempted by the Z’berg-Nejedly Forest Practice Act of 1973 (FPA) (Pub. Resources Code, § 4511 et seq.)2 and the California Timberland Productivity Act of 1982 (TPA) (Gov. Code, § 51100 et seq.). For the following reasons, we conclude that County’s ordinances are not preempted.
A. Overview: State Forestry Law
1. The Forest Practice Act
“Timber harvesting operations in this state must be conducted in accordance with the provisions of the Forest Practice Act. The Act was intended to create and maintain a comprehensive system for regulating timber harvesting [1147]*1147in order to achieve two goals” (Sierra Club v. State Bd. of Forestry (1994) 7 Cal.4th 1215, 1226 [32 Cal.Rptr.2d 19, 876 P.2d 505]): to restore, enhance, and maintain the productivity of timberlands where feasible; and to achieve the maximum sustained production of high quality timber products, while giving consideration to values relating to recreation, watershed, wildlife, range and forage, fisheries, regional economic vitality, employment, and aesthetic enjoyment (ibid.; see § 4513).
As originally enacted in 1973, the FPA permitted individual counties to adopt stricter rules and regulations governing timber operations than those provided under the FPA. (Stats. 1973, ch. 880, § 4, pp. 1615-1616 [adding former § 4516].) In 1982, the Legislature amended the FPA (Stats. 1982, ch. 1561, § 3, pp. 6164-6166) to provide instead that counties may recommend to the California Board of Forestry and Fire Protection (Board) additional forest practice rules and regulations (§ 4516.5, subds. (a), (b)) but, except with respect to performance bonds or other surety for road protection, counties are forbidden to “regulate the conduct of timber operations” (§ 4516.5, subd. (d); hereafter section 4516.5(d)).3
Pursuant to the FPA, “timber operations are controlled by means of a site-specific timber harvesting plan that must be submitted to the [state forestry] department before timber operations may commence.[4] (§§ 4581 and 4582.5.) The Legislature has specified that the plan include the name and address of the timber owner and the timber operator, a description of the land upon which the work is proposed to be done, a description of the silviculture methods to be applied, an outline of the methods to mitigate erosion caused by operations performed in the vicinity of a stream, the provisions, if any, to protect any ‘unique area’ within the area of operations, and the anticipated dates for commencement and completion of operations. (§ 4582, subds. (a)-(g).)” (Sierra Club v. State Bd. of Forestry, supra, 7 Cal.4th at p. 1226.) The director of the state forestry department, and the Board on appeal, review timber harvesting plans for compliance with the FPA and applicable regulations. (§ 4582.7.)
[1148]*11482. The Timberland Productivity Act
The TPA, as amended in 1982 (Stats. 1982, ch. 1489, §§ 1-39, pp. 5748-5766), reflects state policy, inter alia, “that timber operations conducted in a manner consistent with forest practice rules adopted by the [Board] shall not be or become restricted or prohibited due to any land use in or around the locality of those operations.” (Gov. Code, § 51102, subd. (b).)5 The TPA seeks to implement that policy “by including all qualifying timberland in timberland production zones.” (Id., § 51103.) “Timberland,” the Legislature has stated, “means privately owned land, or land acquired for state forest purposes, which is devoted to and used for growing and harvesting timber, or for growing and harvesting timber and compatible uses, and which is capable of growing an average annual volume of wood fiber of at least 15 cubic feet per acre.” (Id., § 51104, subd. (f).)
In order to accomplish its purposes, the TPA relies on tax incentives and zoning mandates. The TPA restricts land in certain timberland production zones (TPZ’s) to the growing and harvesting of timber and compatible uses. (See Gov. Code, §§51115, 51118.) In exchange, owners of land in a TPZ benefit by lower property tax valuations that reflect the enforceable statutory restrictions. (See Cal. Const., art. XIII, § 8 [Legislature may tax certain land consistently with use restrictions].)
The TPA’s predecessor statute (Stats. 1976, ch. 176, § 4.5, p. 305) dictated “timberland preserve” zoning for certain “list A” parcels that were assessed for growing and harvesting timber as the highest and best use. (Gov. Code, § 51110.) Exceptions to mandatory zoning of list A properties were permitted where a parcel in fact was not used for timber growing and harvesting, or where the owner contested the zoning and local officials found exclusion to be in the public interest. (Gov. Code, § 51112, subds. (a), (b).) Timberland preserve zoning also was dictated for certain other timberlands, called “list B” parcels, that were not at that time assessed for growing and harvesting [1149]*1149timber as the highest and best use. (Gov. Code, § 51110.1.)6 Exceptions to mandatory zoning of list B properties were permitted only where local officials found exclusion to be in the public interest. (Gov. Code, § 51112, subd. (c).) Initial determinations as to parcels’ placement on list A and list B were to have been completed by 1978. (Id., subds. (a), (b), (c).)
Since 1978, additional timberland production zoning has been initiated by petition of the property owner. (Gov. Code, § 51113.) The TPA also provides for rezoning and for removal of parcels from timberland production zoning. (See id., §§ 51120-51146.)
B. Preemption Principles
The party claiming that general state law preempts a local ordinance has the burden of demonstrating preemption. (See, e.g., Kucera v. Lizza (1997) 59 Cal.App.4th 1141, 1153 [69 Cal.Rptr.2d 582].) We have been particularly “reluctant to infer legislative intent to preempt a field covered by municipal regulation when there is a significant local interest to be served that may differ from one locality to another.” (Fisher v. City of Berkeley (1984) 37 Cal.3d 644, 707 [209 Cal.Rptr. 682, 693 P.2d 261]; see also Great Western Shows, Inc. v. County of Los Angeles (2002) 27 Cal.4th 853, 866-867 [118 Cal.Rptr.2d 746, 44 P.3d 120].) “The common thread of the cases is that if there is a significant local interest to be served which may differ from one locality to another then the presumption favors the validity of the local ordinance against an attack of state preemption.” (Gluck v. City of Los Angeles (1979) 93 Cal.App.3d 121, 133 [155 Cal.Rptr. 435], citing, inter alia, Galvan v. Superior Court (1969) 70 Cal.2d 851, 862-864 [76 Cal.Rptr. 642, 452 P.2d 930].)
Thus, when local government regulates in an area over which it traditionally has exercised control, such as the location of particular land uses, California courts will presume, absent a clear indication of preemptive intent from the Legislature, that such regulation is not preempted by state statute. (See IT Corp. v. Solano County Bd. of Supervisors (1991) 1 Cal.4th 81, 93 [2 Cal.Rptr.2d 513, 820 P.2d 1023].) The presumption against preemption accords with our more general understanding that “it is not to be presumed that the legislature in the enactment of statutes intends to overthrow long-established principles of law unless such intention is made clearly to appear [1150]*1150either by express declaration or by necessary implication.” (County of Los Angeles v. Frisbie (1942) 19 Cal.2d 634, 644 [122 P.2d 526]; accord, People v. Davenport (1985) 41 Cal.3d 247, 266 [221 Cal.Rptr. 794, 710 P.2d 861]; Theodor v. Superior Court (1972) 8 Cal.3d 77, 92 [104 Cal.Rptr. 226, 501 P.2d 234].)7
Moreover, the “general principles governing state statutory preemption of local land use regulation are well settled. ‘The Legislature has specified certain minimum standards for local zoning regulations (Gov. Code, § 65850 et seq.)’ even though it also ‘has carefully expressed its intent to retain the maximum degree of local control (see, e.g., id., §§ 65800, 65802).’ (IT Corp. v. Solano County Bd. of Supervisors[, supra,] 1 Cal.4th [at p.] 89.) ‘A county or city may make and enforce within its limits all local, police, sanitary, and other ordinances and regulations not in conflict with general laws.’’ (Cal. Const., art. XI, § 7, italics added.) ‘ “Local legislation in conflict with general law is void. Conflicts exist if the ordinance duplicates [citations], contradicts [citation], or enters an area fully occupied by general law, either expressly or by legislative implication [citations].” ’ ” (Morehart v. County of Santa Barbara (1994) 7 Cal.4th 725, 747 [29 Cal.Rptr.2d 804, 872 P.2d 143].)
Local legislation is “duplicative” of general law when it is coextensive therewith and “contradictory” to general law when it is inimical thereto. Local legislation enters an area “fully occupied” by general law when the Legislature has expressly manifested its intent to folly occupy the area or when it has impliedly done so in light of recognized indicia of intent. (Great Western Shows, Inc. v. County of Los Angeles, supra, 27 Cal.4th at pp. 860-861.)
C. The Zone District Ordinance
Plaintiffs contend the zone district ordinance is preempted by section 4516.5(d) of the FPA. With exceptions not relevant here, section 4516.5(d) [1151]*1151provides that individual counties shall not “regulate the conduct of timber operations ... or require the issuance of any permit or license for those operations.” As neither ordinance at issue requires the issuance of any permit or license, this case concerns the import of the statutory phrase “conduct of timber operations.”
In Big Creek Lumber Co. v. County of San Mateo (1995) 31 Cal.App.4th 418, 428 [37 Cal.Rptr.2d 159] (Big Creek v. San Mateo), the Court of Appeal held that section 4516.5(d) does not deprive California counties of authority to zone timberland outside TPZ’s for uses other than timber production. The Court of Appeal acknowledged that section 4516.5(d) mandates that the “conduct” of timber harvesting operations be governed exclusively by state law, but held that San Mateo County’s ordinance, which restricted the location of non-TPZ commercial timber harvesting, did not offend the statute because it spoke “not to how timber operations may be conducted, but rather [to] where they may take place.” (Big Creek v. San Mateo, at pp. 424-425.) The court also noted that numerous provisions of California forestry law reveal the Legislature’s intention to preserve local zoning authority. (See id. at pp. 425-426, citing statutes.) Harmonizing the FPA and the TPA, the court concluded that “the Legislature did not intend to preclude counties from using their zoning authority to prohibit timber cutting on lands outside the TPZ’s.” (Id. at p. 426.) For the following reasons, we agree.
1. Traditional local zoning power
Land use regulation in California historically has been a function of local government under the grant of police power contained in article XI, section 7 of the California Constitution.8 “We have recognized that a city’s or county’s power to control its own land use decisions derives from this inherent police power, not from the delegation of authority by the state.” (Devita v. County of Napa (1995) 9 Cal.4th 763, 782 [38 Cal.Rptr.2d 699, 889 P.2d 1019].) And the Legislature, when enacting state zoning laws, has declared its “ ‘intention to provide only a minimum of limitation in order that counties and cities may exercise the maximum degree of control over local zoning matters.’ ” (Ibid., quoting Gov. Code, § 65800.)9
[1152]*1152Thus, “[t]he power of cities and counties to zone land use in accordance with local conditions is well entrenched.” (IT Corp. v. Solano County Bd. of Supervisors, supra, 1 Cal.4th at p. 89.) “In enacting zoning ordinances, the municipality performs a legislative function, and every intendment is in favor of the validity of such ordinances.” (Lockard v. City of Los Angeles (1949) 33 Cal.2d 453, 460 [202 P.2d 38].)
2. Express preemption
In the FPA, the Legislature directed the Board to divide the state into districts (§ 4531) and adopt “forest practice rules and regulations” for each district (§ 4551).10 No timber operations may be conducted without submission of a timber harvesting plan and approval by the Director of Forestry and Fire Protection or by the Board on appeal. (§§ 4581-4582, 4582.7; see generally Big Creek v. San Mateo, supra, 31 Cal.App.4th at p. 424.) And, as noted, while individual counties may recommend regulations to the Board (§ 4516.5, subd. (a)), they may not regulate the conduct of timber operations (§ 4516.5(d)). The question of express preemption turns on whether the field the Legislature has occupied in so providing encompasses the County’s zone district ordinance. (See Morehart v. County of Santa Barbara, supra, 7 Cal.4th at p. 748.) Our primary task when interpreting a statute is to determine the Legislature’s intent. (Brown v. Kelly Broadcasting Co. (1989) 48 Cal.3d 711, 724 [257 Cal.Rptr. 708, 771 P.2d 406].) We turn first to the statutory language, since the words the Legislature chose are the best indicators of its intent. (Adoption of Kelsey S. (1992) 1 Cal.4th 816, 826 [4 Cal.Rptr.2d 615, 823 P2d 1216].)
Section 4516.5(d) contains no express reference to “zoning,” nor does it bar localities in terms from regulating the location of timber operations. Rather, counties are forbidden to “regulate the conduct” of timber operations. As the court in Big Creek v. San Mateo pointed out, in common parlance an ordinance that avoids speaking to how timber operations may be conducted and addresses only where they may take place falls short of being [1153]*1153“a clear attempt to regulate the conduct" thereof. (Big Creek v. San Mateo, supra, 31 Cal.App.4th at p. 424; cf. Desert Turf Club v. Board of Supervisors (1956) 141 Cal.App.2d 446, 452 [296 P.2d 882] [that state has occupied field of horse racing regulation does not deprive county of right to adopt zoning restrictions on placement of racetracks].) Nevertheless, as the Court of Appeal below recognized, to the extent zoning by definition may have the consequence of excluding logging from some locations, it may in that sense be said to “regulate” that activity, at least in the excluded locations.
When as here a statute is susceptible to more than one reasonable interpretation, “we look to ‘extrinsic aids, including the ostensible objects to be achieved, the evils to be remedied, the legislative history, public policy, contemporaneous administrative construction, and the statutory scheme of which the statute is a part.’ ” (Hoechst Celanese Corp. v. Franchise Tax Bd. (2001) 25 Cal.4th 508, 519 [106 Cal.Rptr.2d 548, 22 P.3d 324]; see also IT Corp. v. Solano County Bd. of Supervisors, supra, 1 Cal.4th at p. 98.) In this case, such indicia support the construction of section 4516.5(d) adopted by the Court of Appeal in Big Creek v. San Mateo, supra, 31 Cal.App.4th 418.
First, in many places where it addresses timberland zoning, general state forestry law expressly preserves and plainly contemplates the exercise of local authority. The actual designation of TPZ’s, for example, is left to local action. (Gov. Code, § 51104, subds. (a), (c), (g); see, e.g., id., §§ 51112 [on or before March 1, 1977 (list A); on or before March 1, 1978 (list B)] and 51113 [current].) Owners of parcels desiring TPZ zoning must petition local authorities. (Id., § 51113, subd. (a)(1).) If the parcel does not meet state timber stocking standards and forest practice rules, the owner must agree to do so within five years (id., subd. (c)(3)(A)), and, if the owner fails to do so, local authorities are empowered to rezone the parcel (ibid.) and to “specify a new zone for the parcel, which is in conformance with the county general plan and whose primary use is other than timberland” (id., subd. (c)(3)(B)). Additionally, local bodies are authorized in certain circumstances to rezone TPZ parcels (Gov. Code, § 51120, subd. (c)) or convert them to another use (id., § 51133, subd. (b)).
“Thus, it is clear that the Legislature has deferred a number of important zoning decisions to local authority, even in the case of TPZ’s.” (Big Creek v. San Mateo, supra, 31 Cal.App.4th at p. 425.) Certainly neither the TPA nor the FPA suggests localities are restricted in what uses they may prohibit outside TPZ zones. (Big Creek v. San Mateo, at p. 428.) “Nowhere in the statutory scheme,” in fact, “has the Legislature expressly prohibited the use of zoning ordinances” (id. at p. 425).
[1154]*1154Second, section 4516.5(d)’s terminology is not “so overshadowing that it obliterates all vestiges of local power as to a subject where municipalities have traditionally enjoyed a broad measure of autonomy.” (Waste Resource Technologies v. Department of Public Health (1994) 23 Cal.App.4th 299, 306 [28 Cal.Rptr.2d 422] [discussing authority to grant refuse disposal permits].) That the Legislature intended the phrase “regulate the conduct” in section 4516.5(d) to preclude only local regulations that affect how timber operations are conducted is borne out by the kinds of issues the Board, under the rubric of “the conduct of timber operations,” is in its rules and regulations statutorily required to address. (See § 4551.5.) Fire prevention and control, soil erosion control, site preparation, water quality and watershed control, flood control, disease prevention and control (ibid.)—these clearly are matters relating to the process of carrying out timber operations. (See Big Creek v. San Mateo, supra, 31 Cal.App.4th at p. 426.)
Third, the legislative history of the FPA does not support plaintiffs’ expansive reading of section 4516.5(d). Although plaintiff Big Creek suggests the Legislature’s purpose was to substitute for local regulation procedures whereby the Board would adopt rules addressing local concerns, the available legislative history contains “no discussion of county zoning authority or its relation to regulation of the ‘conduct’ of logging operations.” (Big Creek v. San Mateo, supra, 31 Cal.App.4th at pp. 426-427.)
Of greater import is that section 4516.5(d) was added to the FPA during the same legislative session in which the TPA was amended. (See Stats. 1982, ch. 1561, § 3, p. 6164 [adding § 4516.5] and id., ch. 1489, §§ 1-39, pp. 5748-5766.) That the Legislature would, in the same legislative session, include in one general forestry statute numerous provisions that rely upon local zoning authority (see, e.g., Gov. Code, §§ 51113, 51133, 51120) and when amending another general forestry statute forbid localities’ exercise of such authority seems unlikely. (See Garvey v. Byram (1941) 18 Cal.2d 279, 282 [115 P.2d 501] [concerning reenactment of former Pol. Code, § 3817 with minor amendments during the same legislative session in which former Pol. Code, § 3834.25 was enacted]; People v. Black (1982) 32 Cal.3d 1, 7-8 [184 Cal.Rptr. 454, 648 P.2d 104] [provisions relating to same subject enacted at same legislative session should be consistently construed].)
The history of the legislation that added section 4516.5(d) to the FPA confirms that one of its purposes was to influence local zoning agencies in the exercise of their authority. A TPZ designation puts county residents on notice that timber operations are expected to occur on the parcel (Gov. Code, § 51115.1, subd. (b)), inter alia to discourage expansion of urban services into timberland (id., §51102, subd. (a)(3)). By restricting timber harvesting to timberland production, mineral extraction industrial, and park, recreation and [1155]*1155open space zone districts, County’s zone district ordinance encourages non-TPZ timberland owners who desire to harvest their timber to rezone their property to one of these permitted zone districts. This in turn advances the Legislature’s objective of “including all qualifying timberland in timberland production zones” (id., § 51103).
Fourth, construing section 4516.5(d) so as to encompass every local regulation of timber operations without regard to whether the regulation purports to control the process or manner of carrying out such operations would not account for the Legislature’s having included the phrase “the conduct of’ in the FPA’s express preemption provision. As the United States Supreme Court has reminded us, “ ‘each phrase within [an express preemption provision] limits the universe of [local action] pre-empted by the statute.’ ” (Lorillard Tobacco Co. v. Reilly (2001) 533 U.S. 525, 550-551 [150 L.Ed.2d 532, 121 S.Ct. 2404], italics added.) Plaintiffs’ proposed reading of section 4516.5(d) would give the phrase “the conduct of’ no limiting effect on the universe of local action preempted by that statute.
Plaintiffs’ reading of section 4516.5(d) also would violate the fundamental rule that “[c]ourts should give meaning to every word of a statute if possible, and should avoid a construction making any word surplusage” (Arnett v. Dal Cielo (1996) 14 Cal.4th 4, 22 [56 Cal.Rptr.2d 706, 923 P.2d 1]). One effect of plaintiffs’ reading would be to render the FPA’s definition of “timberland” (see § 4526) partly surplusage. As previously noted, for the purposes of the FPA (with exceptions not pertinent), “timberland” means “land . . . which is available for, and capable of, growing a crop of trees of any commercial species used to produce lumber and other forest products” (ibid.). The phrase “available for” would be superfluous if the definition were read to include any land that is capable of growing qualified trees, but that is what plaintiffs implicitly urge by suggesting that section 4516.5(d) displaces counties’ traditional power to declare which parcels among all those capable of growing trees are available for timbering.
When the Legislature wishes expressly to preempt all regulation of an activity, it knows how to do so. For example, the Legislature has provided in the TPA that “[p]arcels zoned as timberland production [i.e., located in TPZ’s] shall be zoned so as to restrict their use to growing . . . timber and to compatible uses. The growing and harvesting of timber on those parcels shall be regulated solely pursuant to state statutes and regulations.” (Gov. Code, § 51115, italics added.) One implication of this provision, of course, is that the growing and harvesting of timber on non-TPZ parcels need not be regulated solely pursuánt to state statutes and regulations.
[1156]*1156Moreover, to read section 4516.5(d) as precluding all local zoning control over timber operations could lead to absurd results. Such a reading, for example, apparently would require cities and counties to allow commercial logging even in residential districts. Neither the language of the statute nor its legislative history supports such a reading. (See Big Creek v. San Mateo, supra, 31 Cal.App.4th at p. 427.)
The Legislature has had ample opportunity over the past decade to amend section 4516.5(d) to abrogate or modify the Court of Appeal’s construction of the statutory phrase “regulate the conduct of timber operations” in Big Creek v. San Mateo. Yet, notwithstanding it has amended the FPA in numerous other particulars every year since that decision was filed, it has not done so. Several California judicial decisions, moreover, have relied on Big Creek v. San Mateo in the intervening years.11 “ ‘Where a statute has been construed by judicial decision, and that construction is not altered by subsequent legislation, it must be presumed that the Legislature is aware of the judicial construction and approves of it.’ ” (Wilkoff v. Superior Court (1985) 38 Cal.3d 345, 353 [211 Cal.Rptr. 742, 696 P.2d 134].) The Legislature’s failure to amend section 4516.5(d), while not conclusive, “may be presumed to signify legislative acquiescence” in the Big Creek v. San Mateo decision. (People v. Leahy (1994) 8 Cal.4th 587, 604 [34 Cal.Rptr.2d 663, 882 P.2d 321], citing numerous authorities.)12
[1157]*1157For the foregoing reasons, we agree with the Court of Appeal in Big Creek v. San Mateo that “the ‘conduct’ of timber harvesting operations is exclusively governed by state law. ‘Conduct’ [however] is not given a specialized definition in the FPA. Its ordinary meaning is ‘the act, manner, or process of carrying out (as a task) or carrying forward (as a business, government, or war).’ ” (Big Creek v. San Mateo, supra, 31 Cal.App.4th at p. 426.) Accordingly, local zoning ordinances, like the County’s zone district ordinance, that speak to the location of timber operations but not to the manner in which they are carried out, are not expressly preempted by section 4516.5(d).
3. Implied preemption
The Legislature’s “preemptive action in specific and expressly limited areas weighs against an inference that preemption by implication was intended elsewhere.” (IT Corp. v. Solano County Bd. of Supervisors, supra, 1 Cal.4th at p. 95; see also Cippolone v. Liggett Group (1992) 505 U.S. 504, 517 [120 L.Ed.2d 407, 112 S.Ct. 2608] [“Congress’ enactment of a provision defining the pre-emptive reach of a statute implies that matters beyond that reach are not pre-empted”].) In addition, and specifically pertinent here, “[preemption by implication of legislative intent may not be found when the Legislature has expressed its intent to permit local regulations. Similarly, it should not be found when the statutory scheme recognizes local regulations.” (People ex rel. Deukmejian v. County of Mendocino (1984) 36 Cal.3d 476, 485 [204 Cal.Rptr. 897, 683 P.2d 1150].)
Both these bars to implied preemption are present. By expressly preempting local regulations targeting the conduct of timber operations, section 4516.5(d) implicitly permits local regulations addressed to other aspects of timber operations. And, as has been explained, general forestry law—in particular, the TPA—expressly recognizes local zoning authority. Notwithstanding we might, therefore, forgo applying the test for implied preemption applicable when state statutes do not recognize local regulations, applying that test buttresses our conclusion that County’s ordinances are not preempted.
“In determining whether the Legislature has preempted by implication to the exclusion of local regulation we must look to the whole purpose and scope of the legislative scheme.” (People ex rel. Deukmejian v. County of Mendocino, supra, 36 Cal.3d at p. 485.) Implied preemption occurs when: (1) general law so completely covers the subject as to clearly indicate the matter is exclusively one of state concern; (2) general law partially covers the [1158]*1158subject in terms clearly indicating a paramount state concern that will not tolerate further local action; or (3) general law partially covers the subject and the adverse effect of a local ordinance on transient citizens of the state outweighs the possible municipal benefit. (Ibid.)
(a) Complete coverage
Plaintiffs contend the Legislature has demonstrated its intent to preempt all local restrictions on timber harvesting by fully occupying the field of timber harvesting regulation. Plaintiffs first note the Legislature’s statement of intent, when enacting the FPA, “to create and maintain an effective and comprehensive system of regulation and use of all timberlands.” (§ 4513.) Invoking the maxim expressio unius est exclusio alterius, they argue that certain provisions of the FPA recognizing limited local authority to regulate timber operations indicate that local authority is otherwise preempted.13 But as County points out, the Legislature adopted section 4513 at the same time it adopted a provision authorizing counties to adopt timber harvest rules and regulations stricter than the state’s rules (Stats. 1973, ch. 880, § 4, pp. 1615-1616 [adding former § 4516]), so the general statement of intent in section 4513 cannot have been intended to preempt local restrictions by occupying the field.
Moreover, plaintiffs’ “expressio unius” argument implicitly assumes the statutory preemption of local rules that regulate the conduct of timber operations encompasses geographic zoning restrictions on the location of such operations. But because, as demonstrated, section 4516.5(d) does not have that broad meaning, the Legislature had no need to exempt traditional county zoning power from the section’s preemptive scope; hence, the presence of statutory exceptions to FPA preemption demonstrates nothing about the Legislature’s intent respecting counties’ exercise of that power.
To summarize, general forestry law preempts local regulation of the conduct of timber operations but otherwise expressly contemplates retention of local zoning authority. “[LJocalities must designate certain lands as TPZ’s. These zones are dedicated to timber growing and harvesting, and localities may not prohibit logging on them. As to other lands that may contain timber, the TPA expressly reaffirms local authority to choose appropriate zoning. Local legislative bodies retain authority to exclude from the TPZ’s certain [1159]*1159parcels when they believe exclusion is in the public interest. [Citation.] Localities also retain the authority to choose the non-TPZ zones into which excluded or removed parcels are placed.” (Big Creek v. San Mateo, supra, 31 Cal.App.4th at p. 428.)
We observe, further, that California’s Planning and Zoning Law (Gov. Code, § 65000 et seq.) contemplates the continuation of local government’s traditional zoning authority in connection with timber resources. In adopting that law, the Legislature specified that localities should “exercise the maximum degree of control over local zoning matters” (id., § 65800), inter alia by designating the “location and extent of the uses of the land” (id., § 65302, subd. (a)) and including the “conservation, development, and utilization of. . . forests” in their general plans (id., subd. (d)). The Planning and Zoning Law also requires counties to adopt in their general plans land use elements that “[designate, in a land use category that provides for timber production those parcels of real property zoned for timberland production pursuant to the [TPA]” (§ 65302, subd. (a)(1), italics added), thus implicitly acknowledging the potential for locally designated land use categories that do not provide for timber production.
In sum, this is not a case in which “the subject matter [of where logging can occur] has been so fully and completely covered by general law as to clearly indicate that it has become exclusively a matter of state concern.” (People ex rel. Deukmejian v. County of Mendocino, supra, 36 Cal.3d at p. 485.)
(b) Partial coverage/paramount state concern
Plaintiffs argue that even if the state has not fully occupied the field of timber operations regulation, it has a paramount interest in determining the location of such operations. They point to the FPA’s requirements that the Board adopt rules and regulations governing the conduct of timber operations (§ 4551.5), that any person seeking to conduct timber operations submit and have approved a timber harvesting plan (§ 4581), and that such plans contain a “description of the land on which the work is proposed to be done” (§ 4582, subd. (c)). They point also to the Board’s enactment of several rules that restrict the harvesting activities that may be conducted in particular types of terrain.
We disagree with plaintiffs that either the Legislature’s having directed the Board to adopt rules governing the conduct of timber operations or the Board’s having adopted such rules, impliedly displaces (any more than it expressly does so) traditional local authority to zone permissible (non-TPZ) locations for timber operations. Surely, “[l]ogging, even when conducted [1160]*1160according to state regulations, may have some impacts properly addressed by the [local] zoning authority. That the state has sought to reduce and control these same occurrences through general regulation does not preempt local zoning control, any more than the state and federal regulation of industrial air pollution would preclude a local zoning authority from relying on air pollution as a reason for excluding industrial plants from residential districts.” (Big Creek v. San Mateo, supra, 31 Cal.App.4th at p. 427.)
The Attorney General reached a similar conclusion over 30 years ago, when addressing analogous circumstances. (See County Zoning Ordinances, 52 Ops.Cal.Atty.Gen. 138 (1969).) Asked whether a Marin County zoning ordinance purporting to bar “commercial logging, mining, quarrying, and drilling, together with all associated uses, activities and structures, in certain areas of the county” (id. at p. 139) was preempted by general state laws (including forestry laws) governing the zoned activities, the Attorney General concluded it was not. “It is true,” the Attorney General reasoned, “that California has numerous laws regulating each of the activities prohibited by the proposed ordinance. However, these laws do nothing to preclude an otherwise valid zoning ordinance which prohibits extraction of the resource in question.” (Id. at pp. 139-140.)
Specifically with respect to “the field of commercial logging” (County Zoning Ordinances, supra, 52 Ops.Cal.Atty.Gen. at p. 140), the Attorney General in evaluating Marin County’s ordinance stated: “The Forest Practice Act [then §§ 4521-4618], together with the forest practice rules . . . comprehensively regulate forest practices [so as to] occupy the entire field [of forest practices] and local ordinances with respect to such general practices, are invalid due to such preemption. ... In our opinion, however, this pre-empted area is not so broad as to invalidate a zoning ordinance which prohibits logging where such prohibition is otherwise reasonable.” (Ibid.)
For similar reasons we conclude that today’s general forestry statutes and regulations fall short of “indicat[ing] clearly that a paramount state concern will not tolerate further or additional local action” (People ex rel. Deukmejian v. County of Mendocino, supra, 36 Cal.3d at p. 485), respecting the location of timber operations.
(c) Partial coverage/adverse effect on transient citizens
Plaintiffs’ overriding concern appears to be that localities may by locational zoning prohibit timber harvesting altogether. The ordinance before us does not have that effect, nor does it appear that any county has attempted [1161]*1161such a result.14 The zone district ordinance permits timber harvesting on parcels zoned timberland production, mineral extraction industrial, and parks, recreation and open space. To require that commercial timber harvesting occur on land in a “timberland production” or other specified zone is no more a ban on timber harvesting than a regulation requiring that industrial land uses occur on land zoned “industrial” is a ban on factories. County concedes that landowners wishing to harvest timber may apply to County for approval to rezone parcels to TPZ and that County may not deny TPZ rezoning to any qualifying parcel (Gov. Code, § 51113, subd. (a)(1)), nor may County prohibit timber harvesting in TPZ’s.15
We previously have explained that a local ordinance is not impliedly preempted by conflict with state law unless it “mandate[s] what state law expressly forbids, [or] forbid[s] what state law expressly mandates.” (Great Western Shows, Inc. v. County of Los Angeles, supra, 21 Cal.4th at p. 866.) That is because, when a local ordinance “does not prohibit what the statute commands or command what it prohibits,” the ordinance is not “inimical to” the statute. (Sherwin-Williams Co. v. City of Los Angeles (1993) 4 Cal.4th 893, 902 [16 Cal.Rptr.2d 215, 844 P.2d 534].) Here, County’s ordinances are not impliedly preempted by conflict with state forestry law because it is reasonably possible for a timber operator to comply with both.
The zone district ordinance does not mandate what general forestry law forbids or forbids what general forestry law mandates. While the forestry laws generally encourage “maximum sustained production of high-quality timber products . . . while giving consideration to” competing values (§ 4513), they do not require that every harvestable tree be cut. Accordingly, County’s zoning ordinance does not conflict with state law simply because it may have the effect of placing some trees, at least temporarily, off limits to logging.16 Nor does it appear the Board has adopted for Santa Cruz, or any other county, rules that comprehensively address appropriate geographical locations within the county for timber harvesting.
In sum, plaintiffs have not identified a clear statement by the Legislature of an intent, when enacting the FPA, to preempt traditional local zoning authority over the location of timber operations. Accordingly, and for all the foregoing reasons, we conclude, as did the Court of Appeal in Big [1162]*1162Creek v. San Mateo, that “the Legislature did not intend to preclude counties from using their zoning authority to prohibit timber cutting on lands outside the TPZ’s” (Big Creek v. San Mateo, supra, 31 Cal.App.4th at p. 426).
D. The Helicopter Ordinance
Like the zone district ordinance’s specification of permissible zone districts for timber harvesting, County’s helicopter ordinance is a locational zoning provision that regulates not how timber operations may be conducted, but rather where they may take place. (See Big Creek v. San Mateo, supra, 31 Cal.App.4th at pp. 424-425.) The helicopter ordinance does not attempt to locally regulate the removal of timber, as it speaks neither to whether nor how helicopters may be used to remove timber. County concedes it lacks authority to prohibit timber removal by helicopters or to regulate the manner in which any such removal is conducted. The helicopter ordinance requires simply that any helicopter staging, loading, and servicing facilities associated with timber operations be located either on a parcel of land zoned for timber harvesting or on a parcel adjacent to such, and within the borders of an approved timber harvesting plan.
Accordingly—and for the reasons reviewed in detail above—the helicopter ordinance is preempted neither expressly by section 4516.5(d) nor impliedly by general state forestry law. In the case of the helicopter ordinance, which County apparently enacted to address citizens’ fears created by helicopters transporting multi-ton logs by air over or near their neighborhoods, and citizen concerns with throbbing and unbearable noise, the conclusion is buttressed by the fact that both the FPA and the TPA expressly contemplate the survival of localities’ power to abate nuisances endangering public health or safety. (See especially Pub. Resources Code, § 4514; Gov. Code, § 51115.5, subds. (a), (b).)
Specifically, the FPA provides that “[n]o provision of [the FPA] or any ruling, requirement, or policy of the [B]oard is a limitation on ... the power of any city or county or city and county to declare, prohibit, and abate nuisances.” (Pub. Resources Code, § 4514, subd. (a).) And the TPA provides that, while timber operations conducted within a TPZ pursuant to the FPA “shall not constitute a nuisance” (Gov. Code, § 51115.5, subd. (a)), that limitation is inapplicable to any timber operation that “endangers public health or public safety or . . . prohibits the free passage or use of any navigable lake, river, bay, stream, canal, or basin, or any public park, street, or highway” (id., subd. (b)). (See also Civ. Code, § 3479 [definition of nuisance closely mirrors language preserving nuisance-abatement power in Gov. Code, § 51115.5, subd. (b)].)
[1163]*1163
Disposition
For the foregoing reasons, we reverse the judgment of the Court of Appeal and remand the cause for further proceedings consistent with our opinion.
George, C. J., Chin, J., and Corrigan, J., concurred.